The bank will tell you what you qualify for. That number is always too high. Here's how to calculate what you can actually afford without destroying your financial life.
The #1 homebuying mistake: lenders approve loans based on maximum debt-to-income thresholds — not on what lets you live comfortably, save for retirement, or handle emergencies. A pre-approval letter for $500,000 doesn't mean you should spend $500,000. It means the bank believes you can make the payment. That's a very different thing.
The 28/36 Rule
This is the most widely-used guideline for how much housing you can responsibly afford:
28% — Housing ratio: your total housing payment (PITI: principal, interest, taxes, insurance) should not exceed 28% of gross monthly income.
36% — Total debt ratio (DTI): all monthly debt payments combined (housing + car + student loans + credit cards) should not exceed 36% of gross monthly income.
DTI Examples (Gross $5,000/month)
| Other Debts/mo | Housing/mo | Total DTI | Verdict |
| $400 (car + student loans) | $1,400 | 36% | Great — most lenders approve |
| $800 (high debt) | $1,400 | 44% | Borderline — many lenders decline |
| $400 (car + student loans) | $1,800 | 44% | Too high — reduces loan options |
How to Calculate Your Real Number
Follow these 5 steps in order.
- 1. Calculate your gross monthly income — use pre-tax income. If self-employed, use a 2-year average from your tax returns. Example: $80,000/year = $6,667/month gross.
- 2. Find your max housing payment (28% rule) — multiply gross monthly income by 28%. This is your maximum PITI. Example: $6,667 × 28% = $1,867/month max housing.
- 3. Check your total DTI (36% rule) — add all monthly debt payments (car, student loans, credit cards). Total debts + housing should be under 36%. Example: $6,667 × 36% = $2,400 max total debt; if you have $500/month in debts, housing max drops to $1,900.
- 4. Back-calculate your home price — use a mortgage calculator with your target payment, current rates, expected taxes/insurance to find your max purchase price. Example: at 7%, $1,867/mo P&I supports roughly a $280K loan, plus your down payment = home price.
- 5. Subtract closing costs from your savings — budget 2%–5% of purchase price in closing costs. This comes out of savings in addition to your down payment. Example: $400K home = $8K–$20K in closing costs on top of your down payment.
Down Payment Options
| Down % | Loan Type | Example ($400K) | Key Downside |
| 3% | Conventional (first-time buyer) | $12,000 | PMI required, higher rate, less equity |
| 3.5% | FHA Loan | $14,000 | Mortgage insurance for life of loan (often) |
| 10% | Conventional | $40,000 | PMI still required |
| 20% | Conventional — ideal | $80,000 | Large upfront cash required |
| 0% | VA Loan (veterans only) | $0 | Must be eligible veteran/service member |
PMI — What It Is and When It Ends
Private Mortgage Insurance (PMI) is required on most conventional loans where you put less than 20% down. It's one of the most misunderstood homebuying costs.
- PMI protects the lender (not you) if you default.
- It costs roughly 0.5%–1.5% of the loan amount per year.
- On a $360K loan at 1%, that's $300/month added to your payment.
- PMI cancels automatically once you reach 20% equity (by law — Homeowners Protection Act).
- You can request cancellation early if you hit 20% equity via appreciation + paydown.
- FHA loans have their own version (MIP) that often lasts the life of the loan — a big cost difference.
Key Takeaways
- The bank will approve you for more than you should borrow. Their max is not your max.
- Apply the 28/36 rule: housing under 28% of gross income, all debt under 36%.
- Down payment below 20% means PMI — budget for it and know when it ends.
- Always factor in closing costs (2–5% of purchase price) as a separate savings goal from your down payment.