How to Underwrite a Real Estate Investment

What underwriting actually means

Underwriting is the process of verifying that a deal's numbers and risks are real before you commit money. Banks underwrite loans; smart investors underwrite deals. The goal isn't to fall in love with a property — it's to try to kill the deal, and only buy it if it survives.

Good underwriting answers four questions: How much will it really earn? How much will it really cost? What can go wrong? And does the financing structure survive if it does?

Step 1 — Verify the income, don't trust the listing

Start with the rent. Pull comparable rentals for the same bedroom count and condition within the same neighborhood — not the citywide average. If the property is suited for Section 8 tenants, check the HUD Fair Market Rent for the ZIP code and the local housing authority's payment standard: voucher rents are published, predictable, and often more reliable than the open market.

Be skeptical of pro-forma numbers in listings. 'Market rent' in a broker's brochure is a sales pitch, not a data point.

Step 2 — Build the real expense stack

List every recurring cost: property taxes (look up the actual assessment, and how it changes after a sale), insurance (get a quote — older homes and certain states surprise people), property management, maintenance reserves, vacancy allowance, utilities you'll cover, HOA if any.

Then add the costs new investors skip: capital expenditures. Roofs, HVAC and water heaters die on a schedule. Setting aside $100-$200 per month for CapEx isn't pessimism — it's the price of owning a building.

Step 3 — Stress-test the financing

Calculate the DSCR: net operating income divided by annual debt service. Lenders typically require 1.2 or better, and so should you — a DSCR of 1.0 means one bad month puts you underwater. Then re-run the deal with rent 10% lower and expenses 10% higher. If the deal only works with perfect numbers, it doesn't work.

Check your exit too: if rates rise or you need to sell in year two, what does the deal look like? Underwriting isn't just about buying — it's about surviving the hold.

Step 4 — Underwrite the location, not just the building

The same house performs completely differently two miles away. Check crime levels, tenant demand, population and job trends, and — for Section 8 strategies — the local housing authority's payment standards and waiting list. A cheap property in a market nobody wants to live in isn't cheap; it's a trap with a low entry fee.

The underwriting checklist

Before you write an offer, you should have: verified comparable rents, real tax and insurance numbers, a full expense stack including CapEx, a DSCR at or above 1.2 with stress-tested inputs, cash-on-cash return that meets your target, and a location check covering crime, demand and rent trends. If any box is unchecked, you're not underwriting — you're hoping.