How to Analyze a Rental Property Deal: Cap Rate, Cash-on-Cash Return, IRR Explained

The purchase decision is the highest-leverage moment in rental property investing. Everything that follows — cash flow, tax benefits, appreciation, headaches — is downstream of whether you bought right. A property with solid fundamentals at the right price generates returns for decades. A property bought on gut feel or a single metric can bleed money for years before you cut your losses and sell at a discount.

Yet many investors evaluate deals by instinct or by fixating on one number. A "great cap rate" might mask terrible cash flow once you account for debt service. A property with strong year-one cash-on-cash return might produce mediocre total returns when you model the exit. A deal with thin margins might actually be excellent when you factor in depreciation benefits and equity buildup.

You need multiple metrics, and you need to understand what each one measures, what it ignores, and how they interact. This guide walks through the five most important metrics for evaluating rental property deals. Rather than abstract theory, we will use a single worked example that carries through the entire article — so you can see exactly how the same property looks through each analytical lens.

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The Example Property: A 3-Unit Multifamily in Dorchester, MA

Every formula in this article will reference the same deal so you can see how the metrics relate to each other. Here are the numbers:

Purchase and financing:

• Purchase price: $1,100,000
• Down payment: 25% = $275,000
• Closing costs: $18,000 (title insurance, attorney, recording fees, lender fees)
• Immediate repairs: $35,000 (lead paint remediation on one unit, cosmetic refresh on another)
• Total cash invested at closing: $328,000
• Loan amount: $825,000 at 7.0% fixed rate, 30-year amortization
• Monthly mortgage payment (principal + interest): $5,489
• Annual debt service: $65,868

Income:

• Three units rented at $2,800 per month each
• Gross monthly rent: $8,400
• Gross annual rent: $100,800
• Vacancy assumption: 5% = $5,040 per year
• Effective Gross Income (EGI): $95,760

Operating expenses:

• Property taxes: $11,000
• Insurance: $4,200
• Repairs and maintenance reserve: $6,000
• Water and sewer: $3,600
• Trash removal: $1,800
• Management: $0 (self-managed; if you hired a manager at 8%, add ~$7,660)
• Total operating expenses: $26,600

Net Operating Income (NOI): $95,760 − $26,600 = $69,160

These numbers are realistic for a brick three-decker in the Dorchester neighborhood of Boston in early 2026. Keep them in mind as we work through each metric.

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Cap Rate (Capitalization Rate)

The formula:

Cap Rate = Net Operating Income ÷ Purchase Price

Our example:

$69,160 ÷ $1,100,000 = 6.29%

The cap rate measures the property's annual return on its total value, completely independent of how you finance the purchase. It is the return you would earn if you bought the property entirely with cash. This makes it useful for comparing properties against each other on a level playing field — a property with a 6% cap rate in Boston and a property with an 8% cap rate in Worcester can be directly compared without worrying about different down payments or interest rates.

Cap rate is also a market indicator. In high-demand, low-risk markets like Boston, San Francisco, or Manhattan, cap rates tend to be lower (4-6%) because investors accept lower current yields in exchange for appreciation potential and stability. In secondary and tertiary markets with more risk or less demand, cap rates run higher (7-10%+). A cap rate below 4% in a cash-flow market is a warning sign. A cap rate above 10% may signal either a great deal or a property with problems the market is pricing in.

The key limitation of cap rate is that it ignores financing entirely. In a world where most investors use leverage, the cap rate tells you nothing about your actual cash returns. Our example property has a respectable 6.29% cap rate, but as you will see in the next section, the actual cash-on-cash return after debt service tells a very different story. Cap rate also provides a static, single-year snapshot — it does not model how the investment performs over time as rents increase, expenses change, or the property appreciates.

Use cap rate for quick screening and market comparison. Do not use it as your sole decision metric.

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Cash-on-Cash Return

The formula:

Cash-on-Cash Return = Annual Pre-Tax Cash Flow ÷ Total Cash Invested

First, calculate the annual cash flow:

• Net Operating Income: $69,160
• Annual debt service (mortgage P&I): $65,868
• Annual pre-tax cash flow: $69,160 − $65,868 = $3,292

Then calculate the return:

$3,292 ÷ $328,000 = 1.00%

One percent. That number might make you want to close this article and buy index funds instead. But before you do, understand what cash-on-cash is actually measuring and why it looks so different from the cap rate.

Cash-on-cash return measures how much annual cash income you earn relative to the actual cash you put into the deal — your down payment, closing costs, and repair budget. Unlike cap rate, it accounts for your financing costs. And in a high interest rate environment (7% in our example), financing is expensive. Nearly all of the property's NOI is consumed by debt service, leaving only $3,292 in annual cash flow on a $328,000 investment.

This is not unusual for properties purchased in 2025-2026 at current rates. When 30-year mortgage rates were 3-4% in 2020-2021, cash-on-cash returns of 8-12% were achievable on similar properties. At 7%, the math compresses dramatically. Many experienced investors who built their return expectations in the low-rate era find current deals disappointing by the cash-on-cash metric alone.

What cash-on-cash misses is equally important. It ignores three significant sources of return: equity buildup from principal paydown on the mortgage (in year one, roughly $10,800 of your $65,868 in debt service payments goes toward principal — that is equity you are building), property appreciation (even modest 2-3% annual appreciation on a $1.1M property adds $22,000-$33,000 per year to your net worth), and tax benefits (depreciation deductions, especially with REP status and cost segregation, can produce real after-tax returns that dwarf the pre-tax cash flow).

A property with 1% cash-on-cash but $34,000 in annual depreciation that offsets your W-2 income at a 35% tax rate generates approximately $11,900 in tax savings — effectively tripling the economic return beyond what cash-on-cash reveals.

What is considered a "good" cash-on-cash return depends on the interest rate environment and your investment thesis. In the current market, 4-6% is respectable, and 8% or above is excellent. Below 3%, the deal needs other compelling attributes (strong appreciation potential, tax benefits, below-market purchase price) to justify the thin cash flow.

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Debt Service Coverage Ratio (DSCR)

The formula:

DSCR = Net Operating Income ÷ Annual Debt Service

Our example:

$69,160 ÷ $65,868 = 1.05

DSCR measures how comfortably the property's income covers its debt payments. A DSCR of 1.0 means NOI exactly equals debt service — every dollar of net income goes to the mortgage with nothing left over. A DSCR of 1.05 means NOI exceeds debt service by 5%, which provides an extremely thin margin of safety.

This metric matters for two audiences: your lender and you.

Lenders use DSCR as a primary underwriting criterion for investment property loans. Most lenders require a minimum DSCR of 1.20 to 1.25, meaning the property must generate 20-25% more income than the mortgage payment. Our example property at 1.05 would not meet typical lending requirements, which means the investor would likely need a larger down payment (to reduce the loan amount and therefore the debt service) or would need to negotiate a lower purchase price to get the DSCR above the lender's threshold.

As an investor, DSCR is your stress test. A DSCR of 1.05 means one vacant unit, one major repair, or one month of non-payment tips the property into negative cash flow. What happens if vacancy runs 10% instead of 5%? That drops EGI by another $5,040, reducing NOI to $64,120 — which now falls below the $65,868 debt service. The property is cash-flow negative. A DSCR of 1.25 or above gives you a buffer to absorb these normal fluctuations without dipping into reserves.

Think of DSCR as the answer to the question: "How wrong can things go before this property costs me money each month?" At 1.05, the answer is "barely wrong at all." At 1.30, you have meaningful room for vacancy spikes, unexpected repairs, or temporary rent concessions.

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Gross Rent Multiplier (GRM)

The formula:

GRM = Purchase Price ÷ Annual Gross Rent

Our example:

$1,100,000 ÷ $100,800 = 10.91

The Gross Rent Multiplier is the simplest and bluntest metric in real estate analysis. It answers one question: how many years of gross rent would it take to equal the purchase price? Lower is better — it means you are paying less per dollar of rent.

GRM is useful as a first-pass filter when scanning listings. If you know that multifamily properties in your target market typically trade at 8-12x GRM, a listing at 15x is probably overpriced relative to its income (unless there is a clear value-add opportunity to raise rents significantly). Conversely, a listing at 7x warrants a closer look — either it is a good deal or there is something wrong the GRM is not capturing.

The limitations are severe enough that GRM should never be a decision metric. It ignores all expenses (a property with a great GRM but sky-high taxes and insurance might have terrible NOI), ignores vacancy (it uses gross rent, not effective rent), and ignores financing. A low GRM with high operating costs can be a worse investment than a higher GRM with low expenses.

Use GRM to quickly screen and compare listings. Then use the other four metrics for actual analysis.

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Internal Rate of Return (IRR)

The formula:

IRR is the discount rate that makes the net present value of all cash flows — the initial investment, annual cash flows during the hold period, and the net proceeds from sale — equal to zero. Unlike the other metrics, IRR cannot be solved with simple arithmetic. It requires iterative calculation (Newton-Raphson method or similar), which is why IRR is the metric most likely to require a calculator or software.

Our example — modeling a 7-year hold:

• Year 0 (initial investment): −$328,000
• Year 1 cash flow: $3,292
• Year 2: $3,947 (assuming 3% annual rent growth, relatively stable expenses)
• Year 3: $4,635
• Year 4: $5,358
• Year 5: $6,119
• Year 6: $6,919
• Year 7: $7,762

For the exit, assume 2% annual property appreciation. After seven years, the property value grows from $1,100,000 to approximately $1,264,000. Selling costs at 6% reduce the gross proceeds to approximately $1,188,000. The remaining mortgage balance after seven years of payments is approximately $756,000. Net sale proceeds: roughly $432,000.

Running the IRR calculation across this stream of cash flows (negative $328,000 at the start, modest annual cash flows, and a $432,000 exit windfall in year 7) yields an IRR of approximately 8.5-10%, depending on the exact assumptions for rent growth and expense inflation.

This is dramatically different from the 1% cash-on-cash return. The reason is that IRR captures the full picture: not just annual cash flow, but also equity buildup from principal paydown (roughly $80,000 over seven years) and property appreciation (roughly $164,000 over seven years). Cash-on-cash only sees the thin annual cash flow; IRR sees the entire investment lifecycle.

IRR is considered by sophisticated investors and institutional funds to be the single most comprehensive measure of investment return. It accounts for the time value of money (a dollar received in year 1 is worth more than a dollar received in year 7), incorporates both operating cash flow and exit proceeds, and produces a single annualized percentage that can be compared across entirely different investment types. You can directly compare a rental property's 9% IRR against a stock portfolio's 10% historical return or a private equity fund's 12% target — they are measured in the same units.

The limitations of IRR are its sensitivity to assumptions. Small changes in the exit cap rate, appreciation rate, or hold period can swing the IRR by several percentage points. An IRR of 9% based on optimistic appreciation assumptions and a short hold period is not the same as a 9% IRR built on conservative assumptions. Always test your IRR under multiple scenarios — what if appreciation is only 1%? What if you hold for 10 years instead of 7? What if rents grow at 2% instead of 3%?

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Putting It All Together

Here is our example property through all five lenses:

| Metric | Value | What It Tells You | |---|---|---| | Cap Rate | 6.29% | Moderate unlevered return — reasonable for a Boston-area multifamily | | Cash-on-Cash | 1.00% | Very thin year-one cash flow — tight in the current rate environment | | DSCR | 1.05 | Below typical lender thresholds (1.20+) — limited margin for error | | GRM | 10.91 | In line with metro-area multifamily norms | | IRR (7-year hold) | ~8.5-10% | Attractive total return when appreciation and equity buildup are included |

What story do these numbers tell? The property has solid fundamentals — rents are reasonable for the area, operating expenses are well-controlled, and the long-term return profile is attractive. But the current interest rate environment makes the year-one economics tight. Cash flow barely covers debt service, and a lender would likely want a larger down payment to get the DSCR above their minimum threshold.

An investor might make this deal work in several ways: negotiate the purchase price down to $1,050,000 (improving all five metrics), increase the down payment to 30% (reducing debt service and improving DSCR and cash-on-cash), identify value-add opportunities to raise rents above $2,800 per unit, or accept thin year-one cash flow because the tax benefits of REP status and cost segregation produce $30,000+ in annual tax savings that effectively subsidize the investment.

The critical point is that no single metric tells the complete story. Cap rate and GRM are useful for quick screening — they help you decide which deals are worth a deeper look. Cash-on-cash and DSCR tell you about near-term viability — whether the property will generate cash and comfortably service debt from day one. IRR tells you about total return over the full hold period — whether the deal creates wealth when you zoom out.

The best investors use all five metrics in sequence. GRM and cap rate to screen. Cash-on-cash and DSCR to stress-test near-term viability. IRR to evaluate the total investment thesis. And then they run multiple scenarios — best case, expected case, worst case — to understand how sensitive the returns are to their assumptions.

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Common Mistakes in Deal Analysis

Even experienced investors make analytical errors that lead to overpaying or passing on good deals. Here are the ones we see most often.

Using asking price instead of your offer price. Cap rate and GRM calculated on the listing price are the seller's numbers, not yours. Always calculate metrics based on the price you would actually pay — which should be the result of your analysis, not the input to it. Work backwards: if you need a 7% cap rate, what price produces that cap rate given the property's NOI?

Underestimating expenses. New investors frequently use the seller's provided expense numbers, which may exclude deferred maintenance, undercount management costs (even if you self-manage, your time has value), or assume unrealistic insurance rates. Build your own expense model from comparable properties, actual insurance quotes, and current tax assessments. A 10% error in expenses on a $100,000 NOI property swings the cap rate by roughly 0.5 to 0.7 percentage points.

Ignoring vacancy. A property that is currently fully occupied will not remain so forever. Standard practice is to assume 5-8% vacancy for well-located multifamily properties and 8-12% for higher-risk areas or property types. Using 0% vacancy because "the property has never been vacant" is not analysis — it is hope.

Confusing cap rate with cash-on-cash. These metrics answer different questions and will produce different numbers on the same property whenever leverage is involved (which is almost always). A property with a 6% cap rate might have a 2% cash-on-cash return at 7% interest, or a 10% cash-on-cash return at 3.5% interest. The cap rate did not change — the financing did. Know which metric you are using and what it is telling you.

Fixating on one metric. An investor who only looks at cap rate will miss the cash flow disaster caused by high interest rates. An investor who only looks at cash-on-cash will pass on deals that are excellent on a total-return (IRR) basis. Use the full toolkit.

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What to Do Next

If you have been evaluating deals on napkins or single-metric gut checks, the framework above gives you a systematic approach. Start collecting the actual data — real rent comparables, verified operating expenses, current insurance quotes, actual tax assessments — and plug them into the formulas. The difference between analyzing a deal with real numbers and analyzing it with assumptions is the difference between investing and speculating.

For deals you are seriously considering, model at least three scenarios: a conservative case (lower rents, higher vacancy, higher expenses), an expected case (your best estimates), and an optimistic case. If the deal works in the conservative case, you have a strong investment. If it only works in the optimistic case, you are taking more risk than you may realize.

You can run these calculations by hand, in a spreadsheet, or with purpose-built software. Brickfolio's offer calculator is free to use without an account for quick analysis, and the full deal analysis pipeline supports scenario comparison, three-point estimates, and reverse-calculation for more thorough evaluation.