Real Estate Investment Insights — rental underwriting notes and calculators

Real Estate Investment Insights is for people who already know that cap rate is NOI over price and still get hurt by insurance quotes, post-sale tax bills, and listing rents. We publish working guides, a glossary that distinguishes lender DSCR from a website ratio, and calculators that show the arithmetic of the numbers you type.

The interactive tools use simplifying assumptions — including a blended 1.5% of price expense plug on several screens. That plug is a first pass, not an operating statement. AI “verdicts” group your inputs; they are not appraisals and not a live market feed.

Start with a document, not a dashboard

  1. Underwrite a rental before the listing photos talk you into it — A working underwriting sequence for small residential rentals: lock rent, rebuild expenses from bills, then decide whether leverage still helps.
  2. Twelve checks that should change the offer — or kill it — A short pre-offer checklist for rental buyers. Each item is something that should move price, terms, or a walk-away, not a 50-point ritual.
  3. The expense stack the 50% rule hides — Where the 50% nickname hides real carrying costs on small rentals — taxes after a sale, insurance, turnover — and the worksheet that replaces it.

Then open the mortgage calculator or Deal Analyzer and replace the pretty rent with leased comps. Read About for how the Site is run, Contact for corrections, and the disclaimer before you treat any figure as a plan. Privacy and ads: Privacy Policy.

Eight free calculators

All of them are free and none needs an account. The quick deal check at the top of the page sends a price and a monthly rent straight into the Deal Analyzer, so you can see a first cut in seconds and then fix the inputs that were guesses.

How to use this site on a real property

Start with rent. Asking rents on listing sites run ahead of what a unit actually leases for, so pull two or three signed leases for similar units nearby, or ask a local property manager what they would list it at. Use the lower number.

Then rebuild the expenses from paper. Get an insurance quote for the address, not a statewide average. Look up how the county reassesses after a sale, because the seller's tax bill is often not the one you will pay. Add a vacancy allowance, a repair reserve and capital expenses for the roof, HVAC and water heater based on their age. If a manager will run it, put their fee in even if you plan to self-manage for now.

Only after that does financing belong in the picture. Run the payment on the rate and points you were actually quoted, then check whether the property still pays its own way. If it only works with the best-case rent and the lowest possible expenses, it doesn't work. The Scenario Simulator is there to show how thin the margin gets when one or two of those numbers move against you.

Last, walk the pre-offer checklist. Each item on it should change the price, the terms or your willingness to buy at all. If an item wouldn't change any of those, it isn't on the list.

Due-diligence tools from our homeowner network

The Investor's Brief

Occasional, education-first notes on underwriting, financing and due diligence. One email a week at most, and you can unsubscribe anytime.

Nothing here is financial, legal or tax advice. The guides explain how the numbers fit together; a lender, a CPA and a local attorney should check any deal before you sign.

Articles live at /blog. Older outline-shaped posts now carry field notes on the parts those outlines usually skip.