Rule 1: The 28% Gross Income Rule
The 28% rule states: your total monthly housing payment (PITI) should not exceed 28% of your gross monthly income. At $80,000/year gross, maximum PITI = $1,867/month. At today's rates and prices, a $1,867 PITI supports a home price of only about $230,000 — far below the national median of $430,000. The 28% rule was calibrated when home prices were much lower relative to incomes.
28% rule tested against 2025 national median home price reality
| Income | 28% Max PITI | Home Price Supported (7%, 30yr, 10% dn) | National Median ($430K) Status |
|---|---|---|---|
| $60,000 | $1,400 | $185,000 | Well below median — most markets not feasible |
| $80,000 | $1,867 | $255,000 | Below median — limited market options |
| $100,000 | $2,333 | $325,000 | Below median — works in lower-cost markets |
| $120,000 | $2,800 | $395,000 | Near median — broad market access |
| $150,000 | $3,500 | $500,000 | Above median — comfortable nationally |
The 28% rule eliminates most buyer options in markets where median prices exceed $350,000. In practice, most new homebuyers in 2025 pay 32 to 40% of gross income for housing. Use it as a comfort benchmark, not a rigid ceiling. Many buyers safely exceed 28% with financial discipline.
Rule 2: Buy 3x Your Annual Income
The 3x income rule says do not buy a home priced above 3 times your annual gross income. At $100,000/year, max purchase = $300,000. The national median is $430,000. At current rates, buying the median home requires 4.3x income. The 3x rule made sense when rates were 5% and medians were $200,000. At today's rates and prices, 4x to 5x income is the realistic range for buyers in average markets.
The 3x rule is a useful lower bound for checking if a purchase is clearly safe, but it is not a realistic ceiling in 2025. At $100,000 income, 3x = $300,000 — well below the national median. The more useful test: does the PITI payment fit within your actual take-home budget with room for savings and emergencies?
Rule 3: Save 20% Down Before Buying
The 20% rule avoids PMI and gets the best rate tier. But on a $430,000 national median home, 20% = $86,000. For a household saving $1,500/month toward a down payment, reaching $86,000 takes nearly 5 years — during which the home price may appreciate 15 to 25%. The opportunity cost of waiting often exceeds the PMI savings.
Cost of waiting for 20% down vs. buying now with 5% — national median scenario
| Scenario | Action | Home Price at Purchase | PMI Cost (5 yrs) | Appreciation Missed |
|---|---|---|---|---|
| Buy now at 5% down | Buy $430K with $21,500 down | $430,000 | $12,900 | $0 missed |
| Wait 5 yrs for 20% down | Save $86K over 5 years | $524,000 (at 4%/yr) | $0 PMI | $94,000 missed appreciation |
| Net advantage of buying now | — | — | PMI cost $12,900 | Appreciation gained $94,000 |
Rule 4: Keep Your Mortgage Under 15 Years
Dave Ramsey and other personal finance educators advocate for 15-year mortgages exclusively. The interest savings are genuinely enormous ($250,000 to $400,000 on a median-priced home). But the payment requirement eliminates this option for many buyers. The 15-year payment on a $344,000 loan (national median with 20% down) at 6.375% is $2,978 — requiring $127,629/year income under the 28% rule. The rule is mathematically correct but practically inaccessible for many households.
Rule 5: Housing Should Not Exceed 30% of Take-Home Pay
The 30% of take-home rule is more practically useful than the gross income version because it is based on what you actually have available. On $100,000/year gross, take-home is approximately $6,600/month (after taxes, 401k, insurance). 30% of take-home = $1,980/month — a manageable housing budget in many markets. This rule is more realistic than the gross income version for day-to-day budgeting.
Rule 6: The 1% Annual Maintenance Rule
Budget 1% of home value annually for maintenance. On a $430,000 home, that is $4,300/year ($358/month). For older homes (20+ years), 1.5 to 2% is more realistic. For newer construction with active warranties, 0.5% may suffice in the first 5 years. Of all the mortgage rules of thumb, this one is the most consistently applicable regardless of rates, prices, or income levels.
The 1% maintenance rule has never been more relevant than in today's market. Deferred maintenance compounds. Ignoring a $400 gutter cleaning becomes a $4,000 fascia repair becomes a $40,000 foundation issue. Budget 1% annually — every year — without exception.
Updated Rules for 2025 Reality
Classic mortgage rules updated for 2025 market conditions
| Original Rule | 2025 Adjustment | Why the Change |
|---|---|---|
| 28% gross income max PITI | 32 to 38% is common — use as comfort floor, not hard ceiling | Home prices rose faster than incomes since 2000 |
| 3x income max purchase | 4 to 5x is functional reality in average markets | Price-to-income ratios nationally at historic highs |
| 20% down required | 5 to 10% is now typical; PMI math often favors buying sooner | PMI cost vs. appreciation opportunity cost has shifted |
| 15-year only | 20-year is an excellent middle ground that fits more budgets | Payment threshold more realistic for 20yr vs. 15yr |
| 30% of take-home | Still valid — most practical affordability benchmark | Based on actual cash flow, not gross |
| 1% maintenance | Remains fully valid — 1.5% for older homes | Repair costs rise with inflation |
Test the Rules Against Your Real Numbers
Enter your income, target price, and down payment — see exactly which rules your scenario satisfies.