Strategy

How to analyze a rental property, step by step

Updated 2026-08-26

Every rental analysis, whatever the tool, is the same five steps: estimate the income, subtract the operating expenses, layer on the financing, compute the return metrics, and compare them to your standards. This article walks the whole chain with a live worked example, edit any input below and watch every downstream number move.

The chain, in two formulas

NOI = Effective Gross Income − Operating Expenses

Cash Flow = NOI − Debt Service

Everything else (cap rate, cash-on-cash, DSCR) is a ratio built from these two lines.

Step 1: Income

Start from market rent, not the seller's number, use comparable listings or a rent-comp tool, and be suspicious of a pro-forma that assumes a rent no neighbor achieves. Then haircut it for vacancy (5% is a common baseline; use your market's). Rent × 12 minus vacancy is your Effective Gross Income (EGI).

Step 2: Operating expenses

Itemize, don't guess: property taxes (public record, pull the actual bill), insurance (get a quote), repairs and capex reserves (commonly ~5% of gross rent each), and management (~8 to 10% of collected rent, count it even if you self-manage). The 50% rule is a fine placeholder for this whole block, but replace it with real lines before you offer. EGI minus these is your NOI: the mortgage is not an operating expense.

Step 3: Financing

Loan amount = price minus down payment; the monthly principal & interest comes from the standard amortization formula. Financing is where thin deals die at today's rates, which is why a screen that ignores it (like the 1% rule) can't make the decision.

Steps 4 & 5: Metrics, then verdict

Four numbers carry most of the weight: monthly cash flow (what's left after everything), cash-on-cash return (cash flow against the actual dollars you put in), cap rate (the unlevered yield), and DSCR (whether the property covers its own mortgage, lenders typically want ≥ 1.2). Then judge them against your thresholds (your buy box) not someone else's.

Work one now

Underwrite it 0/3

Set the market rent
Enter the real tax bill
Run the numbers

That's a complete underwrite, income to verdict. Every number below traces back to your inputs.

Worked example: rental underwrite

Purchase price

Market rent / mo

Property taxes / yr

Insurance / yr

Down payment %

Interest rate %

Before you trust any result: stress it. Rate +1%, rent −$100, one extra vacancy month. A deal that survives all three is a deal.

Doing this at volume

One property, by hand, takes an evening the first time. The investors who find good deals screen dozens, which is the entire case for tooling. In BuyBox, a Quick Analysis runs this whole chain from an address in about 30 seconds, scores the result 0 to 100 against your buy box, and flags what fell short, and you can hover any number to see the formula and inputs behind it, exactly like the math lines above. Your first 7 days are a free trial: 3 Deep Dives and 10 Quick Analyses, no card required.

Run your first deal analysis in 30 seconds

Open BuyBox, run a Quick Analysis, and read your first deal verdict, try the real controls below, or watch it done.

The 1% rule: a 10-second screen, not an underwrite

The 1% rule says a rental's monthly rent should be at least 1% of its total acquisition cost. Here's how to use it, and exactly where it falls apart.

The 50% rule: estimating expenses before you have real numbers

The 50% rule estimates that a rental's operating expenses will average about half of its gross rent, everything except the mortgage. Useful for a first pass; dangerous as a final answer.