When preparing to buy a home, the most dangerous question you can ask a bank is "How much can I borrow?" The bank's calculation is designed to determine the maximum risk they are willing to take, not what is comfortable for your daily life.

To determine how much house you can truly afford, you must look beyond the bank's approval and analyze your own budget.

The Bank's Formula: Debt-to-Income (DTI)

Lenders evaluate your affordability using the Debt-to-Income (DTI) ratio. They look at your gross (pre-tax) monthly income and compare it to your total monthly debt obligations (car payments, student loans, credit cards, plus the new mortgage).

Most lenders will approve a loan as long as your total debt obligations do not exceed 43% to 45% of your gross income. Some programs allow up to 50%.

The Problem with the Bank's Math

The bank uses your gross income (before taxes), but you pay your mortgage with your net income (after taxes). The bank also doesn't know about your childcare costs, grocery bills, retirement contributions, or vacation funds.

If you borrow the absolute maximum the bank allows, you risk becoming "house poor"—having a beautiful home but no cash left over to actually enjoy life or handle emergencies.

The Practical Rules of Affordability

To find a comfortable price range, financial experts suggest several rules of thumb:

1. The 28/36 Rule

This classic rule states that:

  • Your total housing costs (PITI + HOA) should not exceed 28% of your gross monthly income.
  • Your total debt (housing + all other debt) should not exceed 36% of your gross monthly income.

2. The 25% Net Income Rule

A more conservative approach used by some financial advisors is to cap your total housing payment at 25% of your take-home (net) pay. Because it is based on the money that actually hits your checking account, this rule leaves plenty of room in the budget for investing and living expenses.

Calculating the Real Cost

When determining affordability, you must calculate the total monthly payment, not just the loan repayment.

Use our Mortgage Calculator to estimate:

  • Principal and Interest
  • Property Taxes
  • Homeowners Insurance
  • PMI (if putting less than 20% down)
  • HOA Fees

Finally, factor in maintenance. A good rule of thumb is to budget 1% of the home's value per year for maintenance and repairs. (For a $300,000 home, expect to spend about $3,000 a year, or $250 a month, fixing things).