A mortgage calculator tells you what your payment will be. It doesn't tell you whether that payment is actually affordable for your specific situation. Those are different questions.
Lenders use debt-to-income ratios to set approval limits. The most common benchmark is the 28/36 rule. Your monthly housing costs shouldn't exceed 28% of your gross monthly income, and your total monthly debt payments shouldn't exceed 36%. A lender will approve you up to these limits.
Getting approved for a loan amount doesn't mean that loan amount is the right choice for your situation. Lenders are evaluating risk of default. They're not evaluating whether the payment leaves you with enough breathing room to save, handle unexpected expenses, or maintain your actual quality of life.
The mortgage payment is just the start. Property taxes vary significantly by location and can add hundreds per month to your housing cost. Homeowners insurance is required by lenders and adds more. If your down payment is under 20%, private mortgage insurance (PMI) is typically required until you reach 20% equity.
Then there's maintenance. A reasonable estimate is 1% of the home's value per year for ongoing upkeep and repairs. On a $350,000 home, that's $3,500 annually, or roughly $290 per month budgeted over time. Older homes and larger homes tend toward the higher end. This cost is invisible until something breaks, and something always eventually breaks.
HOA fees apply to many condos and planned communities and can range from modest to significant depending on the development. Utilities in a larger home will almost certainly run higher than in your current place. These costs add up and they're all real.
Start with your take-home pay, not gross income. Lenders use gross income because that's the standard measure, but your bills get paid with what actually lands in your account after taxes and any deductions.
Add up the realistic total monthly cost of homeownership for the property you're considering: mortgage payment, property taxes, insurance, PMI if applicable, HOA if applicable, and a maintenance reserve. Compare that total against your take-home pay. If it consumes more than 30% to 35% of take-home income, the math gets tight.
Use the Calculon mortgage calculator to nail down the principal and interest portion, then add the other costs on top. Running the full number before you're emotionally attached to a specific property is easier than running it after.
20% down eliminates PMI and reduces the loan principal, which lowers both the monthly payment and total interest paid. It also requires significantly more cash upfront, which means either a longer savings runway or buying a less expensive home.
Putting less down is not automatically a mistake. If you have stable income, plan to stay in the home for several years, and PMI costs are reasonable relative to the alternative of waiting longer to save, buying with less down can make sense. The decision depends on your specific situation, local market conditions, and how much financial cushion you'll have left after closing.
Buying at the top of what you're approved for is tempting. It's a bigger house, often in a better location. But being house-poor, having most of your income committed to housing costs with little flexibility for anything else, is a genuinely uncomfortable way to live. It also leaves you vulnerable if income drops or an unexpected expense arrives.
The approval limit is a ceiling. Where you buy within that range is up to you.
Calculate the true monthly cost of ownership, not just the mortgage payment. Compare it against take-home income, not gross. Leave room for maintenance, life, and the unexpected. Lenders will tell you the maximum they'll lend. That number and the right number for your situation are often not the same.
Further reading coming soon.