Most people have to finance a house in order to buy it. Of course, some shrewd budgeters — especially those who are nearing retirement — have a paid-off house, so when they go to sell it, they pocket the money and can pay cash for the next one.

Ultimately, most people want to know how much the monthly payment will be, and that's a function of the length of mortgage you choose (15 years versus 30 years, for example), your down payment, and the prevailing interest rate.

To help you find out how much of a monthly payment you'll end up owing, use one of several online mortgage calculators that are available. You can find out everything from how much your monthly payment will be to how much of a difference the mortgage length, down payment, and interest rate make.

Don't forget to add on the cost of PMI (private mortgage insurance) and escrow to the monthly bill. Although not everyone has to pay these costs, if you do, they will be added to your monthly payment amount.