The free analysis takes ten seconds. It tells you if a listing is even worth a second look. The full model is the same underwriting I've used on commercial deals for 22 years — vacancy, taxes, reserves, NOI, cap rate, cash-on-cash, DSCR — before you write the offer.
Listing price, down payment, rent. The same first-pass I run before I spend an hour on a deal. Then keep scrolling — the full model is waiting.
Leave one unit's rent blank if you'd live in it — the analysis treats that as your house-hack unit.
What the napkin says
Your Real Monthly Housing Cost
$0/ mo
Gross rent minus the mortgage. This is the number most buyers fall in love with.
This number is incomplete on purpose.
It ignores vacancy, maintenance, capital reserves, and what it actually costs to close. Lenders do not ignore those. Neither should you.
See what a full underwriting analysis looks likeExample numbers, based on what you entered above — not a real listing or financial advice.
A copy-paste prompt that finds currently listed 2–4 unit properties matching your parameters — on ChatGPT, Claude, Gemini, or any AI you already use (web browsing turned on). Built for your first deal.
Your first deal will probably come from a listed property. This prompt maps the brokers and firms who see 2–4 unit listings before — or instead of — the portals, and hands you the exact questions to ask when you call.
The word-for-word script for calling the brokers and agents Prompt 2 finds you. No blanks to fill in — print it and keep it next to the phone.
The 7 steps to buying your first 2–4 unit property, in order — with both prompts built into the steps where you need them. Printable. Keep it.
Download the PDFFound a listing worth a second look? Run it through the analyzer above — then verify it with The Deal Verifier before you offer.
That's a real swing, every month, on a single listing. Vacancy, maintenance, and reserves were never optional — the napkin just declined to count them.
Same example numbers as above — illustrative, not a real listing.
Napkin math
$0
Full underwrite
$0
Monthly, after every cost. Left is rent minus the mortgage. Right is NOI minus debt service.
Where the money actually goes
Lender-grade metrics
Stress it before you offer
Move them. Watch DSCR and cash-on-cash change. The full workbook lets you set every line from your real tax bill, insurance quote, and rent roll.
Property manager
8% of collected income after vacancy
You're not buying a calculator. You're buying the line items a lender, an appraiser, and a serious principal will actually check — packaged so you can run them yourself in under five minutes.
Most property calculators spit out a number and call it a day. This is a workbook you keep — Excel, Google Sheets, or Numbers — and run on every listing until you find one that actually works.
Seven years of this deal
Illustrative 3% appreciation plus principal paydown and the model's cash flow. Not a promise — a picture of why underwriting the hold matters as much as month one.
Unlimited properties. One payment. The first deal you skip because the model said no is the one that pays for this a hundred times over.
Get The Deal Verifier — $47Toggle it on the free analysis above — leave a unit blank to house-hack it, or fill every unit to run it as a pure rental. The workbook keeps both views, so you can see what it costs to live there, or what it pays you as a rental, before you choose.
House hack
The other unit's rent isn't "cash flow." It's a reduction in what it costs you to live. The model shows your real monthly housing cost after vacancy, taxes, insurance, and reserves — the easiest way to start the move from labor to capital.
Pure investment
Monthly and annual cash flow, cap rate, cash-on-cash, DSCR. The numbers that tell you if it's a deal or a mistake — the same analysis, run the same way, whether this is your first duplex or your fifth.
A cap rate that "sounds fine" is how suburban duplexes get priced like trophies. The gold line on the chart is this listing, underwritten with the assumptions you set above.
Figures are illustrative closed-sale ranges from 2025–2026 market reports (Northmarq, Matthews, Kidder Mathews, ARCA / CoStar). Your property is not an average — that's the point of running the model.
California & U.S. multifamily
Secure checkout via Stripe. You'll be redirected to your download immediately after purchase.
Hi, I'm Arthur DeJohn. 20+ years in commercial real estate, underwriting income properties for investors and brokers.
I built this because most first-time buyers run the numbers on a property the same way they'd guess a tip — and the ones who don't have a framework are the ones who find out they overpaid after closing, not before.
This is the same framework I've used with real clients for two decades, packaged so you can run it yourself in under 5 minutes.
Use it once. See what it tells you about your next deal.
The question isn't whether you'll find a listing. It's whether you'll know if it's actually a good one when you do.
Get The Deal Verifier — $47Instant download • 7-day guarantee • Yours forever
