Q. I want to build a $124,000 house. I make around $40,000 a year and have credit scores from 619 to 629. My wife is in school and she will have a job in a few months. She has credit scores between 667 and 693 but no income yet. All I have to pay monthly is a few credit cards and some school loans which average $150 altogether and three payments left on my truck. Would I qualify for a mortgage with no down payment?

Probably not. With a credit score near 620 -- the cutoff for being considered a subprime or high-risk borrower -- you're unlikely to qualify for 100% financing. A rash of foreclosures has prompted lenders to start demanding at least minimal down payments from all borrowers with sub-prime credit scores. And any loan you might qualify for will come with a high interest rate -- anywhere from 7.2% to 8.8% according to Fair Isaac Corp., which created the formula for calculating FICO credit scores.

If you spend the next six months raising your credit score closer to 700, you'll have a much better chance to qualify for the amount you need at a rate closer to 5.75%, about the average for 30-year fixed-rate loans right now. That could shave close to $70 a month off your payments.

Just paying off your truck should boost your credit score and lower your debts -- another critical factor in determining how much you can afford to borrow.

Your wife will also be out school and working. That will boost your income and also make it easier to obtain all the money you need at a more affordable rate.

Whether you're buying a home or refinancing an existing mortgage, we have a mortgage calculator that can help you make the right decisions.