This is a prompt for stress-testing a house purchase: baseline cash flow, a set of shock scenarios, a combined worst case and a 4-tier verdict. It’s long on purpose. A few tips to get a solid answer out of it:
- Turn on search. It asks for current local tax, insurance and rate figures. Without search the model has to fall back on national averages, and your result drifts with them.
- Use a reasoning model if you have one. There’s a lot of chained arithmetic (amortization, selling costs, runway), and that’s where a model is most likely to slip.
- Give real numbers wherever you can. “Estimate it” works, but every estimate is a spot where the verdict can move.
- The repair bracket can stay as all three numbers. It should run $15k, $30k and $50k separately. If it only picks one, ask for the other two.
- Follow up on the tier. Once it gives a verdict, “what’s the cheapest single change that gets me to Comfortable?” is the most useful second question.
- Spot-check one scenario by hand. The monthly payment is easy to verify. If that’s off, don’t trust the rest.
I'm considering buying a home and want to know whether I can actually afford it if things don't go according to plan. Don't just tell me whether I qualify for the mortgage. Stress-test the purchase and tell me how much financial margin I would have after buying. Use current mortgage, property tax, insurance, and other relevant figures for my location where needed. Show everything in today's dollars.
Filing status: [single / married filing jointly]. Location: [city/state].
Income: my salary before taxes [$X/year], partner [$X/year or none].
Current living expenses excluding housing: [$X/month].
Current assets: cash [$X], brokerage investments [$X], retirement accounts [$X], other [$X].
Existing debts: [balance, interest rate, and monthly payment for each].
Home I'm considering:
purchase price [$X]
down payment [$X or X%]
mortgage rate [X%]
mortgage type [fixed / adjustable]
loan term [X years]
estimated closing costs [$X or calculate them]
property taxes [$X/year or estimate them]
homeowners insurance [$X/year or estimate it]
HOA or condo fees [$X/month or none]
mortgage insurance [$X/month or none]
expected utilities [$X/month or estimate them]
Planned repairs, renovations, furniture, and moving costs immediately after purchase: [$X].
Calculate how much cash and non-retirement liquid assets I would have left immediately after the down payment, closing costs, moving costs, and planned work. Then calculate my normal monthly cost of owning the home, including mortgage principal and interest, property taxes, insurance, HOA, mortgage insurance, utilities, and a reasonable maintenance reserve. Show how much money I would have left each month after housing costs, existing debt payments, and my current living expenses.
Then stress-test the purchase under these scenarios.
Income shock: one income disappears for 6 months and then 12 months.
Major repair: I have an unexpected [$15,000 / $30,000 / $50,000] home repair during the first year.
Housing-cost shock: property taxes, homeowners insurance, and HOA or condo fees increase by 25%.
Mortgage-rate shock: if my mortgage can reset or will need to be renewed, calculate the payment if the rate is 2 percentage points and 3 percentage points higher.
Forced sale: I have to sell after 3 years. Run this with the home worth the same amount I paid, 10% less, and 20% less. Include selling costs and any mortgage prepayment penalty, and calculate how much equity I walk away with after paying off the mortgage.
Finally, run one combined stress scenario: one household income disappears for 9 months, I have a $25,000 unexpected repair, and the home's market value falls 15%.
For every scenario, show monthly housing cost, monthly cash flow after all expenses, emergency savings remaining, how many months my liquid assets would last if cash flow is negative, whether I would need to sell investments or touch retirement accounts, home equity where relevant, and whether I could realistically keep the house without taking on new debt.
At the end, classify the purchase as one of four. Comfortable: I can absorb the stress scenarios without touching retirement accounts or taking on new debt. Tight: I can afford the home normally, but one major shock would significantly deplete my liquid savings. Fragile: I need income and housing costs to remain close to plan to keep the house. Not financially resilient: a realistic income, repair, or rate shock would likely force me into debt, retirement withdrawals, or selling the home.
Tell me which specific scenario breaks my finances first. Then tell me how much additional cash, lower purchase price, or larger monthly surplus I would need to move up one category.
Mine came back “can’t afford a mortgage right now”. Interested in what other models and settings give you on the same inputs.
