How Much House Can I Afford? A Complete Breakdown by Income and Debt
The answer to “how much house can I afford?” is not a number. It is a formula — and most people are applying it wrong. They look at the monthly payment, see it fits their budget, and call it affordable. But they have not accounted for property taxes, insurance, maintenance, HOA fees, or what happens to that budget when the water heater fails and the roof needs replacing in the same year. This article gives you the full math: the lender's calculation, the real-world affordability calculation, and 12 income-level scenarios at two rate environments so you have a concrete anchor before you start shopping.
The Lender's Calculation: What the Bank Will Approve
Lenders use two debt-to-income ratios to determine how much they will lend you:
- Front-end DTI (28% rule): Your monthly PITI (principal, interest, taxes, insurance) should not exceed 28% of gross monthly income. Some lenders allow up to 31%.
- Back-end DTI (36% rule): All monthly debt payments (PITI plus car loans, student loans, credit cards, child support, etc.) should not exceed 36% of gross monthly income. Conventional lenders often allow up to 43%; FHA allows up to 50% with compensating factors.
The lower of these two constraints determines your actual limit. If you have no other debt, the front-end 28% typically binds. If you have significant debt, the back-end 36% binds — and your housing budget shrinks accordingly.
Affordability by Income: 12 Scenarios at 6.75% and 7.5% Rates
These scenarios apply the 28% front-end rule to monthly gross income, then back into a purchase price using current rate assumptions. Property taxes assume 1.2% annually (national average). Insurance assumes 0.5% annually. PMI (for under 20% down) adds 0.8% annually. Scenarios show 10% down (with PMI) and 20% down (no PMI).
Rate Environment 1: 6.75% 30-Year Fixed (Mid-2025 to Early 2026 range)
| Annual Income | Max PITI/mo | Max Price (10% down) | Monthly Payment | Max Price (20% down) | Monthly Payment |
|---|---|---|---|---|---|
| $50,000 | $1,167 | $148,000 | $1,163 | $165,000 | $1,162 |
| $60,000 | $1,400 | $177,000 | $1,395 | $198,000 | $1,394 |
| $75,000 | $1,750 | $221,000 | $1,745 | $247,000 | $1,742 |
| $90,000 | $2,100 | $266,000 | $2,096 | $297,000 | $2,093 |
| $100,000 | $2,333 | $295,000 | $2,326 | $330,000 | $2,326 |
| $120,000 | $2,800 | $354,000 | $2,793 | $396,000 | $2,790 |
| $150,000 | $3,500 | $443,000 | $3,494 | $495,000 | $3,489 |
| $175,000 | $4,083 | $517,000 | $4,078 | $578,000 | $4,073 |
| $200,000 | $4,667 | $591,000 | $4,661 | $660,000 | $4,652 |
| $250,000 | $5,833 | $738,000 | $5,825 | $825,000 | $5,812 |
Rate Environment 2: 7.5% 30-Year Fixed (Higher Rate Scenario)
| Annual Income | Max PITI/mo | Max Price (10% down) | Max Price (20% down) | vs. 6.75% Ceiling |
|---|---|---|---|---|
| $50,000 | $1,167 | $135,000 | $152,000 | -$13K / -$13K |
| $75,000 | $1,750 | $202,000 | $227,000 | -$19K / -$20K |
| $100,000 | $2,333 | $270,000 | $302,000 | -$25K / -$28K |
| $150,000 | $3,500 | $405,000 | $454,000 | -$38K / -$41K |
| $200,000 | $4,667 | $540,000 | $605,000 | -$51K / -$55K |
| $250,000 | $5,833 | $675,000 | $755,000 | -$63K / -$70K |
A 0.75% rate increase reduces your maximum purchase price by roughly $20,000-$70,000 depending on income level — without changing your income or down payment. This is why rate changes have such a direct impact on housing market activity.
Run your exact numbers — with your actual income, down payment, and local tax rate — using the MoneyLens mortgage calculator.
How Existing Debt Reduces Your Housing Budget
The scenarios above assume zero other debt. Most buyers have some: car loans, student loans, credit card minimums. Here is how common debt loads reduce maximum purchase price on a $100,000 income at 6.75% with 10% down:
| Existing Monthly Debt | Available for Housing (36% rule) | Max Purchase Price | Reduction vs. No Debt |
|---|---|---|---|
| $0/month | $2,333 (28% limit binds) | $295,000 | baseline |
| $200/month (small car) | $2,200 (36% limit: $3,000 - $200 = $2,800; 28% = $2,333) | $279,000 | -$16,000 |
| $400/month (mid car) | $2,133 (36% limit: $3,000 - $400 = $2,600; but 28% still limits) | $270,000 | -$25,000 |
| $600/month (car + student loans) | $2,400 (36%: $3,000 - $600 = $2,400; now back-end binds) | $303,000 if only back-end applied | 28% still limits; net $295K |
| $800/month (heavy debt load) | $2,200 (36%: $3,000 - $800 = $2,200; back-end now binds) | $279,000 | -$16,000 |
| $1,000/month (very heavy) | $2,000 (36%: $3,000 - $1,000 = $2,000) | $253,000 | -$42,000 |
| $1,500/month (maxed out) | $1,500 (36%: $3,000 - $1,500 = $1,500) | $190,000 | -$105,000 |
A $1,500/month debt load on a $100,000 income reduces your maximum purchase price by $105,000 — from $295,000 to $190,000. This is why paying down car loans before applying for a mortgage is standard financial planning advice, not just noise.
The Hidden Costs That Break First-Time Buyer Budgets
Lender approval is based on PITI. But actual homeownership costs are higher. Here is a complete cost audit for a $300,000 home purchase in three different scenarios:
| Cost Category | New Construction | 10-Year-Old Home | 30-Year-Old Home |
|---|---|---|---|
| Principal & Interest (6.75%, 10% down) | $1,748 | $1,748 | $1,748 |
| Property Taxes (1.2% of value) | $300 | $300 | $300 |
| Homeowner's Insurance | $125 | $125 | $175 |
| PMI (0.8% with 10% down) | $180 | $180 | $180 |
| HOA (if applicable) | $0-$400 | $0-$300 | $0-$250 |
| Maintenance Reserve (1% annually) | $250 | $300 | $400 |
| Utilities (vs. renting) | +$150 | +$200 | +$300 |
| Total Monthly Cost (no HOA) | $2,753 | $2,853 | $3,103 |
| What Lender Counts as PITI | $2,353 | $2,353 | $2,353 |
| Hidden Cost Delta | +$400 | +$500 | +$750 |
The lender approves you for PITI. Actual ownership costs run $400-$750/month higher — and that is without a major capital expenditure year. Buyers who stretch to their lender ceiling often find themselves cash-poor within 18 months of purchase.
Capital Expenditures: The Budget Item Most Buyers Ignore
Beyond monthly costs, homes require periodic large-ticket replacements. Buyers who do not budget for these are not actually affording the home — they are deferring costs into debt. Here are median replacement costs for the major systems, plus expected lifespans:
| System | Median Replacement Cost | Expected Lifespan | Monthly Reserve |
|---|---|---|---|
| Roof | $8,000-$20,000 | 20-25 years | $33-$83 |
| HVAC (furnace + A/C) | $5,000-$12,000 | 15-20 years | $28-$67 |
| Water Heater | $1,000-$3,500 | 10-15 years | $8-$29 |
| Appliances (full set) | $5,000-$10,000 | 10-15 years | $42-$83 |
| Windows (full replacement) | $8,000-$20,000 | 20-25 years | $33-$83 |
| Plumbing (major repair) | $2,000-$15,000 | Variable | $25-$50 reserve |
| Flooring (full home) | $5,000-$20,000 | 15-25 years | $25-$83 |
| Total Annual Reserve (mid-estimate) | $250-$500/month |
A fully-reserved homeowner should be setting aside $250-$500/month beyond PITI for capital expenditures. For a 20-30 year old home, lean toward the $400-$500 end. Add this to your true affordability calculation — not as an optional savings goal, but as a cost of ownership.
The Real Affordability Number: What You Should Actually Target
Financial planners increasingly advocate for a more conservative threshold than the lender maximum. Here is why: lenders approve you based on your ability to make payments. They are not accounting for your retirement savings rate, childcare costs, emergency fund maintenance, or the career flexibility costs of being locked into a maximum payment. The conservative rule: target a PITI at 25% of gross income (not 28%), and keep total housing costs — PITI plus maintenance reserve, utilities, and HOA — below 30-33% of gross.
On $100,000 income, that means:
- Lender ceiling (28%): $2,333/month PITI → $295,000 purchase price at 6.75% with 10% down
- Conservative target (25%): $2,083/month PITI → $263,000 purchase price
- Comfortable buffer (22%): $1,833/month PITI → $232,000 purchase price
The $63,000 gap between the lender ceiling and comfortable-buffer scenarios represents the financial breathing room to fund your retirement, weather income disruptions, and handle unexpected capital expenditures without going into debt. Most financial planners recommend buying below your lender maximum, not at it.
Run Your Numbers Before You Start Shopping
The tables above give you a range. Your actual ceiling depends on your specific credit score, local property tax rate, insurance premiums, and existing debt. Before you start attending open houses — which creates emotional attachment to specific prices — run your actual numbers:
- Mortgage calculator — exact payment at any price, rate, and down payment
- Loan calculator — model how paying off existing debt changes your DTI ceiling
- Savings goal calculator — see how long it takes to build your target down payment
The single most common financial mistake first-time buyers make: starting with the home search and then reverse-engineering affordability. Start with the math. Let the number determine the search range, not the other way around.
Key Takeaways
- The 28% front-end rule (max housing cost as % of gross income) sets your lender ceiling — but the 25% conservative target gives you breathing room
- Every 0.75% rate increase reduces maximum purchase price by roughly $20,000-$70,000 depending on income
- $1,000/month in existing debt on a $100K income cuts your purchase ceiling by $42,000
- True ownership cost exceeds PITI by $400-$750/month — budget for maintenance, utilities, and capital expenditure reserves
- Lenders approve you for your maximum; financial health requires targeting meaningfully below it