How to Analyze a Rental Property: Cap Rate, CoC & DSCR

To analyze a rental property, build net operating income from verified rent and line-item expenses, then test it four ways: cap rate against the price, cash flow and cash-on-cash return against your financing, DSCR and break-even occupancy against risk, and total return over your holding period. Finally, stress-test the inputs that are most likely to be wrong. This guide walks through each step on one property, a $280,000 duplex.

You can follow along in the US rental property ROI calculator, which computes NOI, cap rate, cash-on-cash, DSCR, and holding-period ROI from the same inputs.

The example property

• Side-by-side duplex listed at $280,000, offered at full price
• Two 2-bedroom units; current leases $1,500 each ($3,000 a month)
• 25% down ($70,000), $210,000 loan at 7.25% for 30 years — conforming loans on 2–4 unit investment properties stop at 75% loan-to-value under Freddie Mac's LTV limits
• Closing costs estimated at 3% ($8,400) and $5,000 of make-ready work
• Cash invested: $70,000 + $8,400 + $5,000 = $83,400

Step 1: Verify the rent before anything else

Rent is the input that moves every metric, so check it three ways:

1. Current leases and payment history. Ask for the leases and 12 months of bank deposits or a rent roll. A lease at $1,500 means little if the tenant pays late or is on a month-to-month term.
2. Comparable listings. Look at similar units within a mile that actually rented, not asking prices.
3. A property manager's estimate. Local managers will often give a rent opinion for free.

If the evidence says $1,400 rather than $1,500, use $1,400. A $150 a month error on this property changes the result from $202 of monthly cash flow to $74, as the stress test below shows.

Step 2: Screen fast with the 1% and 50% rules

Two rules of thumb tell you whether a deal deserves a full analysis:

• 1% rule: monthly rent ÷ price. $3,000 ÷ $280,000 = 1.07%. Passing means the rent is high relative to price; failing does not automatically kill a deal in a high-price, low-tax market.
• 50% rule: assume operating expenses will eat about half of gross rent. $36,000 × 50% = $18,000 of estimated NOI. Compare that with the $17,191 annual mortgage: a thin margin, so continue to the detailed build.

Treat both as filters only. The detailed NOI below comes in at $19,614, about $1,600 better than the 50% estimate, because this duplex has modest taxes and no HOA.

Step 3: Build NOI line by line

The mortgage is not in this table. NOI measures the property; financing is a separate decision.

The capital reserve deserves attention on any multi-unit building: two water heaters, two HVAC systems, two kitchens, and one roof. Estimate the remaining life and replacement cost of each, divide, and sum. $200 a month is $48,000 over 20 years.

Step 4: Check the price with the cap rate

Cap rate = NOI ÷ price = $19,614 ÷ $280,000 = 7.01%.

The cap rate is useful in two directions. As a yield, it tells you the property earns 7 cents per dollar of price before financing. As a valuation tool, it tells you what the property is worth at the cap rates similar buildings trade for locally:

Ask a local agent or appraiser for recent duplex sales and their NOIs. If comparable buildings traded at 7.5%, you are overpaying by roughly $18,500. Gross rent multiplier (price ÷ annual gross rent = 7.78 here) is a cruder cross-check when sellers will not share expenses.

Step 5: Layer in financing — cash flow and cash-on-cash

• Monthly payment on $210,000 at 7.25%: $1,432.57; annual debt service $17,191
• Annual cash flow = $19,614 − $17,191 = $2,424 ($202 a month)
• Cash-on-cash return = $2,424 ÷ $83,400 = 2.91%

That cash-on-cash figure is the yield on your own money before tax. Compare it with what the same $83,400 earns elsewhere at similar risk. A low cash yield can still be acceptable if you value the principal paydown and long-run rent growth, but you should know you are making that trade.

Step 6: Measure risk — DSCR and break-even occupancy

DSCR = NOI ÷ debt service = $19,614 ÷ $17,191 = 1.14. NOI covers the mortgage with a 14% cushion. Below 1.0 the property needs your money every month.

Break-even occupancy shows how much of the potential rent must come in to pay every bill:

• Fixed operating costs (tax, insurance, utilities, repairs, reserve): $11,180
• Debt service: $17,191
• Management takes 9% of whatever is collected, so the property keeps 91% of each rent dollar
• Break-even = ($11,180 + $17,191) ÷ ($36,000 × 91%) = 86.6%

This duplex can lose about 13% of its potential rent — roughly 3.2 unit-months a year, or about 1.6 months per unit, — before cash flow goes negative. A property with break-even occupancy above 95% has almost no room for turnover.

Step 7: Stress-test the assumptions

Change one input at a time, then all at once:

Any single bad surprise leaves the deal cash-flow positive, which is a reasonable margin of safety. Several together turn it negative by about $3,200 a year. Decide whether your reserves could carry that for a year or two. If not, negotiate the price or pass.

Step 8: Estimate total return over your hold

Cash flow is only one part of the return. Over five years, assuming 2% annual appreciation and 6% selling costs:

That is 41.39% on $83,400 invested, or 7.17% a year compounded. Taxes would change it in both directions: depreciation shelters most of the cash flow (year-one taxable income on this duplex is about −$1,289 after $15,158 of interest and $8,145 of depreciation), but the depreciation is taxed at up to 25% when you sell. The after-tax rental cash flow guide explains the annual effect, and the real estate capital gains tax guide covers the sale.

Step 9: Make the call

Write down your hurdle before you analyze, so the numbers cannot talk you into a deal. A simple set of buy rules for this kind of property might be:

This duplex passes, narrowly. The decisive question is the local cap rate for similar buildings: if comparable sales prove 7.5%, offer closer to $262,000.

Common analysis mistakes

• Using the seller's expenses. Owner-managed buildings often report no management, minimal repairs, and an old tax bill.
• Counting the mortgage in NOI. It double-counts financing in cap rate and DSCR.
• Ignoring utilities on older multifamily. Shared water meters are common, and the owner pays.
• Skipping the reserve. The roof and HVAC will come due; the only question is when.
• Analyzing at the asking price only. Solve for the price that meets your rules, then offer that.

Tools for each step

Run the property through the rental property ROI calculator for Steps 3–8. To see whether your income supports the loan, use the investor DTI and borrowing power calculator, and to estimate tax on the annual cash flow, the rental after-tax cash flow calculator.