Lenders are incentivised to approve you for as much as possible — their revenue comes from loan origination fees and interest. The pre-approval limit is their risk ceiling, not your comfort zone. The gap between "what the bank will lend" and "what you can afford without stress" can be substantial.
The standard rules
The 28/36 rule is the classic starting point — but it's a floor, not a target.
The 28/36 rule says your housing costs shouldn't exceed 28% of gross monthly income, and total debt payments shouldn't exceed 36%. These are guideline ratios that lenders use for underwriting, not personal finance optima.
| Ratio | What It Includes | Guideline |
|---|---|---|
| Front-end ratio (housing) | Principal + interest + property taxes + homeowner's insurance + HOA (PITI) | ≤ 28% of gross monthly income |
| Back-end ratio (all debt) | Housing costs + car payments + student loans + credit card minimums + other debt | ≤ 36% of gross monthly income |
| DTI for most conventional loans | Back-end ratio | Up to 43–45% allowed by lenders; 36% is the conservative target |
The real calculation
Work from take-home pay, not gross income.
The 28% gross rule systematically overstates what people can afford because it ignores taxes, retirement contributions, and other essential expenses. A more reliable approach starts with your actual monthly take-home pay.
Start with your monthly take-home pay (after tax and retirement contributions)
This is what actually hits your bank account each month. Use your recent pay stubs — not gross salary — as your baseline.
Real number — what you actually have to allocateList your essential non-housing monthly expenses
Car payments + insurance, groceries, utilities, phone, childcare, student loans, health insurance (if not employer-covered), subscriptions, average dining/entertainment. Be honest — don't use aspirational budgets.
Fixed obligations — subtract before calculating housing budgetSubtract step 2 from step 1 — what's left is your maximum housing budget
This is your real constraint. Many buyers find their comfortable housing number is 20–25% of take-home, not 28% of gross. The gap matters significantly on a 30-year mortgage.
Your real ceiling — not the bank's ceilingFrom that housing budget, account for ALL housing costs — not just mortgage P&I
Property taxes (0.5–2.5% of home value annually depending on state/county), homeowner's insurance (~$100–200/month), PMI if <20% down (~0.5–1.5% annually), HOA if applicable, and estimated maintenance (budget 1% of home value per year).
True cost — mortgage P&I is only part of housing costsThe hidden costs
Most buyers dramatically underestimate the non-mortgage costs of ownership.
On a $400,000 home, here's what the real monthly cost looks like beyond principal and interest at a 7% 30-year rate (~$2,661/month P&I):
| Cost | Estimate | Annual Total |
|---|---|---|
| Mortgage P&I ($400k, 30yr, 7%) | $2,661/month | $31,932 |
| Property taxes (1.2% average) | ~$400/month | $4,800 |
| Homeowner's insurance | ~$150/month | $1,800 |
| PMI (if <20% down, ~0.8%) | ~$267/month | $3,200 |
| Maintenance (1% of value) | ~$333/month | $4,000 |
| Total monthly cost | ~$3,811/month | $45,732 |
The full cost is 43% higher than the mortgage payment alone. A buyer who budgets based on the mortgage payment will find ownership significantly more expensive than expected.
Down payment
20% avoids PMI — but waiting to hit 20% has a cost too.
Avoids PMI entirely. On a $400k home, that's $80,000 down — and no extra $200–300/month in PMI premiums. Best rate tier for conventional loans. Requires significant savings discipline before buying.
PMI required until LTV reaches 80%. PMI can be cancelled once you have 20% equity — either via payments or appreciation. Request cancellation from your servicer; it doesn't happen automatically at 80% LTV (though lenders must cancel at 78% by law under the Homeowners Protection Act).
Lower down payment barrier but FHA MIP (mortgage insurance premium) lasts for the life of the loan if you put less than 10% down — it doesn't cancel like PMI. Refinancing to a conventional loan once you have 20% equity is often the exit strategy.
If you buy with less than 20% down, plan your PMI exit from day one. Track your LTV as you pay down principal and as home values rise. Once you believe you've reached 80% LTV, order a new appraisal and request PMI removal from your servicer. Getting rid of $200–300/month in PMI is the equivalent of refinancing to a significantly lower rate.
Stress test your decision
Before you commit, ask these four questions.
Job loss is the most common trigger for mortgage distress. If your monthly payments require both incomes and you have no buffer, the house may be priced at your absolute limit — not a comfortable one.
Depleting all savings for a down payment leaves you exposed. The first year of homeownership often produces unexpected repair costs. Keep reserves separate from your down payment.
Buying a house should not mean pausing 401(k) contributions permanently. If affordability requires stopping retirement savings long-term, the house may be too expensive for your current financial position.
Transaction costs (agent commissions, closing costs, moving costs) typically run 8–10% of home value round-trip. If you sell in 2–3 years, you may lose money even if home prices rise modestly. Ownership makes financial sense over longer horizons.
Banks and mortgage lenders approve based on their risk tolerance, your credit score, and debt-to-income ratios. They don't know your childcare costs, your career uncertainty, your planned family size, or whether you're funding a retirement account. Pre-approval for $550,000 doesn't mean $550,000 is wise — it means the lender will issue the loan. The right number is yours to determine.
What's your actual comfortable home buying budget?
Franky asks about your take-home pay, existing debts, savings, and goals — then gives you a realistic purchase price range and monthly payment you can live with long-term.
Talk to Franky →