Do the other units cover the mortgage? The house-hack coverage check
Rung 8 of 10 · Cognitive verifier
1 · Learn the move · Cognitive verifier
A house-hacker lives in one unit of a 2-4 and rents the rest, so the honest question isn't 'does it cash-flow' but 'how much of my PITI do the OTHER units cover while I live here?' The cognitive verifier makes AI restate every assumption first, PROVIDED or INFERRED, and surface the verifying questions it can't answer from your inputs (what vacancy? whose utilities? a signed lease or just a comp?) before it sets the coverage up as a formula you compute, not a number it invents. The two traps: counting your own unit's 'rent' as income (you live there), and quietly computing or promising the payment. Coverage is set up and handed to your model; the mortgage stays your lender's number.
Run a house-hack coverage check as a cognitive verifier. Restate my assumptions PROVIDED/INFERRED first. I live in one unit, so only the OTHER units' rent offsets PITI. Set coverage up as a formula tagged COMPUTE IN YOUR MODEL/verify. Don't compute or promise it; use my lender's PITI, invent no rent. Not a lending decision or investment advice.
Compute it — deterministically, no AI
The lesson sets the math up and hands it off. Here's the model it hands it to: real math in your browser, so the number is right and your client is never handed a fabricated one.
Keyroom · Calculator
House-hack coverage
PITI, what the other units cover, and what you'd still pay, the math the coverage lesson hands off.
Your numbers
Every figure is your input. Drag or type. The math runs here — no AI.
The property
The loan
Carrying costs
The rented units
Your client's monthly cost to live here
PITI $3,810 minus the rented units $2,660 (after a 5% vacancy allowance)
See the math
Assumptions
- Owner-occupied: your client lives in one unit; ONLY the other units' rent counts toward covering PITI. The owner's own unit is never counted as income.
- PITI = principal + interest (from price, down, rate, term) + property taxes/12 + insurance/12 + HOA. It excludes PMI/MIP, maintenance, capex, and utilities the owner pays.
- The rent is a comp-based estimate, not a signed lease; a vacancy allowance is applied to keep the coverage honest.
- 'Your monthly cost' is what the owner still pays to live there after the rent offset. Partial coverage is not 'living for free.'
Learn the grounded prompt behind this number: Do the other units cover the mortgage? →
A planning estimate from your inputs, computed here (not by an AI). It excludes mortgage insurance, maintenance, capex, and owner-paid utilities, and the rents are comp estimates, not signed leases. Confirm PITI with the lender and rents with signed leases before relying on it. Not investment or lending advice.
2 · Your turn. You write the prompt
Your client is considering a triplex to owner-occupy: they'll live in Unit 1 and rent Units 2 and 3. Pasted: lender-quoted PITI $2,900/month; achievable rent (from your rental-comp read) about $1,400 per unit for Units 2 and 3. They want a target of covering at least 70% of PITI with the rented units. Vacancy, maintenance, and reserves aren't set. Write a prompt that sets up the coverage check honestly without counting Unit 1 or promising anything.
Remember: the AI sees only your prompt, not this page. If the situation isn't in your prompt, it doesn't exist.
Optional. These shape the output when you run your prompt below, not your score.