How Much House Can I Afford? The Real Numbers Behind Homebuying

Why "How Much Can I Borrow" Is the Wrong Question

When most people start thinking about buying a home, they go straight to a lender, get pre-approved, and take that number as their budget. That's a mistake.

Lenders tell you the maximum they're willing to lend — not the amount that's wise for your life. A bank might pre-approve you for $450,000, but a $450,000 mortgage could strain your budget, eliminate your ability to save, and turn your dream home into a source of constant financial stress.

The right question isn't "how much can I borrow?" It's "how much can I comfortably afford to own?" Those numbers are often very different.

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The 28/36 Rule: A Classic Benchmark

The 28/36 rule is the traditional guideline lenders and financial planners use to assess home affordability:

• 28%: Your total housing payment (mortgage principal + interest + property taxes + homeowners insurance + HOA fees if applicable) should not exceed 28% of your gross monthly income.
• 36%: Your total debt payments — housing plus all other debt (car loans, student loans, credit cards) — should not exceed 36% of your gross monthly income.

Example: If you earn $7,000/month gross:

• Maximum housing payment: $7,000 × 0.28 = $1,960/month
• Maximum total debt: $7,000 × 0.36 = $2,520/month

If you already have $400/month in car and student loan payments, your maximum housing payment under the 36% rule is $2,520 − $400 = $2,120/month.

The 28/36 rule is a starting point, not a law. Some financial advisors use a more conservative 25% cap on housing to leave more room for saving and other priorities. In high-cost cities like San Francisco or New York, buyers routinely stretch beyond 28% — but doing so requires tight discipline everywhere else in the budget.

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Understanding Your DTI Ratio

Your Debt-to-Income (DTI) ratio is the primary metric lenders use to evaluate your mortgage application. It measures your monthly debt obligations as a percentage of your gross monthly income.

Front-end DTI = Housing costs ÷ Gross monthly income

Back-end DTI = All monthly debt payments ÷ Gross monthly income

Most conventional lenders want:

• Front-end DTI: 28% or lower
• Back-end DTI: 43% or lower (though 36% is more comfortable)

FHA loans allow back-end DTI up to 57% in some cases — but just because you can qualify doesn't mean you should borrow that much. A 50%+ back-end DTI leaves very little margin for emergencies, car repairs, or any unexpected expense.

Why it matters: If your back-end DTI is already high from student loans or car payments, you have less room for a mortgage. Paying down other debt before buying a home can dramatically improve what you can comfortably afford.

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Down Payment, PMI, and What Lenders Don't Emphasize Enough

The down payment affects both what you can borrow and how much your loan costs monthly.

The 20% threshold: If you put down less than 20% on a conventional loan, you'll typically pay Private Mortgage Insurance (PMI) — an extra monthly cost of roughly 0.5–1.5% of your loan amount per year. On a $300,000 loan, that's $1,500–$4,500/year ($125–$375/month) that builds no equity and provides no benefit to you.

PMI goes away once you hit 20% equity, but it can add years to the timeline on a smaller down payment.

Common down payment options:

• 20%+: No PMI, better rates, lower monthly payment
• 10–15%: PMI applies, moderate upfront cost
• 5%: PMI applies, lower upfront cost but higher monthly total
• 3% (conventional) or 3.5% (FHA): Minimum options; expect PMI and a higher base mortgage insurance cost

Saving for a 20% down payment on a $350,000 home ($70,000) takes time, but the math often justifies waiting. Run the numbers both ways before deciding to buy sooner with less down.

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The Hidden Costs of Homeownership Nobody Warns You About

The mortgage payment is just the beginning. True monthly homeownership costs include:

Property taxes: Vary wildly by location — from under 0.5% to over 2.5% of the home's assessed value per year. On a $350,000 home in a 1.5% tax rate area, that's $5,250/year ($437/month). Check the specific county before buying.

Homeowners insurance: Typically $100–$200/month depending on home value, location, and coverage level. In flood zones or hurricane areas, this can be significantly higher.

HOA fees: If you're buying in a community with a homeowners association, fees can range from $50/month for a small condo complex to $500+/month for amenity-heavy communities. HOA fees don't reduce; they often increase annually.

Maintenance and repairs: The general rule of thumb is 1–2% of the home's value per year. A $350,000 home could require $3,500–$7,000/year on average in maintenance — new roof, HVAC service, plumbing repairs, appliances, etc. Some years cost nothing. Some years cost $15,000. Budget for it.

Utilities: Larger homes cost more to heat, cool, and maintain. Moving from a 900-sq-ft apartment to a 2,200-sq-ft house can add $200–$400/month in utility costs.

A simple rule: add 35–50% to your principal + interest payment to estimate your true monthly cost of ownership. A $1,800/month mortgage might cost $2,600–$2,900/month all-in.

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How to Calculate Your Real Budget

Work backwards from your take-home pay, not your gross income:

1. Start with your monthly net income (what actually hits your bank account after taxes and contributions).
2. Subtract all existing fixed expenses: car payment, student loans, insurance, subscriptions, etc.
3. Subtract your target savings rate: aim for at least 10–15% of net income toward retirement and emergency fund.
4. Whatever remains is your discretionary pool — what's available for housing plus food, transportation, entertainment, and everything else.
5. Allocate housing from that pool. A sustainable housing payment leaves enough for the rest of your life without constant stress.

Run this exercise before talking to a lender. Walk into the pre-approval conversation knowing your number, not asking for theirs.

Buying a home is one of the most consequential financial decisions you'll make. Understanding the real costs — not just the sticker price — is the difference between building wealth through homeownership and being trapped by it.

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