How to Analyze a Rental Property (Before You Buy It)

Most people analyze a rental backwards: they fall in love with the house, then look for numbers that justify it. Do it the other way. A rental is a small business that happens to have a front door — analyze the business first, and let the numbers tell you whether the house is worth buying. Here's how to do it in five steps, the same way an experienced investor screens a deal.

1. Start with the real rent

Everything flows from rent, so get it right. The number you want is the current market rent — what this specific property would lease for today, not the seller's pro-forma, not what the current tenant pays (which may be under market), and not last year's number. Pull comparable rentals on the same street, same bed/bath count, similar condition. If the seller says $2,600 and the comps say $2,300, underwrite $2,300. Optimistic rent is how good-looking deals turn into bad ones.

2. Subtract vacancy to get what you'll actually collect

No rental is occupied every day of every year. Tenants move out, units sit for a few weeks, and occasionally someone doesn't pay. Budget 5–8% of gross rent for vacancy and credit loss, even in a hot market — it's the difference between gross potential rent and the income you actually bank (your effective income). Skipping it makes every downstream number too rosy.

3. Build the real operating expenses

This is where deals are won or lost, because it's where beginners cut corners. Operating expenses are everything it costs to run the property except the mortgage:

• Property tax — varies enormously by state and even by county; look up the actual assessed amount, don't guess.
• Insurance — get a real quote for a landlord policy, which costs more than an owner-occupied one.
• HOA — if there is one, it's a hard monthly cost.
• Property management — budget 8–10% of rent even if you plan to self-manage. Your time isn't free, and you may not want to be a landlord in year five.
• Maintenance and repairs — the leaky faucet, the broken disposal. Around 5% of rent.
• CapEx reserve — the money you set aside for the roof, the HVAC, the water heater — the $6,000–$10,000 items that don't happen every year but will happen. Around 5% of rent. Skipping the CapEx reserve is the single most common way investors fool themselves into a "cash-flowing" deal that actually bleeds money the year the roof goes.

Add these up and subtract them from your effective income. What's left is net operating income (NOI) — the property's income before financing.

4. Subtract the mortgage to get cash flow

Now bring in the loan. Your monthly cash flow is NOI minus the mortgage payment (principal and interest). Positive means the tenant pays you every month; negative means you subsidize the property out of your own pocket. This is the headline number, and the rental property cash flow calculator runs the entire chain — rent, vacancy, all the expenses, and the mortgage — in one shot so you can see the real figure and change any input to test it.

5. Judge the deal with three numbers

Cash flow tells you whether it works; these three tell you whether it's good:

• Cash-on-cash return — annual cash flow ÷ the cash you invested (down payment + closing + rehab). This is the yield on your money, the number that lets you compare a rental to any other place you could put your capital. Calculate it here.
• Cap rate — NOI ÷ price. It ignores your loan, which makes it the right tool for comparing two properties on equal footing. A rental's cap rate versus the neighborhood norm tells you if you're overpaying.
• The 1% rule — monthly rent ÷ price. A five-second screen: is the rent at least 1% of the price? Check it here. It's not an analysis — it's how you decide what's worth analyzing.

The four ways a rental actually pays you

Cash flow is only the first of four returns, and analyzing just the first one undersells (or oversells) a deal. Over a full hold, a rental builds wealth through cash flow (the rent premium over costs), loan paydown (your tenant retiring your mortgage), appreciation (the property gaining value), and tax benefits (depreciation and deductions). A deal with thin year-one cash flow can still be excellent if rents grow and the loan amortizes; a deal with great day-one cash flow in a declining area can still lose. Analyze cash flow first because it's the one that can kill you fast — but underwrite the whole hold before you decide.

Screen fast, verify slow

The workflow that keeps you sane: use the 1% rule to throw out the obvious no's, run the cash-flow calculator on the maybe's, and only then walk the property and dig into the details on the few that clear both. You'll analyze a hundred deals for every one you buy — and the whole point of running the numbers first is so the house you fall in love with is one that also happens to make money.