Housing affordability calculators are typically based on converting a mortgage interest rate to a monthly amortization payment over 15 or 30 years (whatever the life of the mortgage is). This number is compared with monthly income and a rule of thumb is applied - say, one-third of income is too much to pay for a mortgage payment. That then converts to a maximum mortgage. The size of the mortgage added to the down payment equals the price of the house.
MORTGAGE LIMIT CALCULATOR (HOW LARGE A MONTHLY MORTGAGE PAYMENT DOES YOUR INCOME PERMIT?)
This kind of calculator is also known as a housing affordability calculator. The key input number is monthly income - the lower this is, the lower the mortgage payment you can afford. The higher interest rates go, the less house you can afford. The lower your down payment, the less house you can afford. Take your pick: How Much House Can You Afford? CNNMoney FannieMae, BankRate.com, Yahoo! Real Estate, SmartMoney, HomeFair (Moving.com), HOEPA