Q. With a credit score over 770, what would be the lowest possible down payment on a $175,000 to $190,000 loan? We have financed the entire purchase price of our last three houses with piggyback loans.

A. Although it's harder to qualify for 100% financing than it was a few years ago, you should be able to do it. But here are a few things to consider.

First, piggyback loans don't make much sense right now because second mortgages are so much more expensive that primary mortgages. Most buyers are better off getting a single loan and paying for private mortgage insurance.

Even a small down payment, just 5% or 10%, would allow you to qualify for the best rate most lenders offer. If you finance the entire purchase price, expect to pay a quarter- or half-point more for your loan.

And finally, be very careful if you live in an area where home prices are declining. In a couple of years you could end up owing more on your mortgage than your house is worth.

We see that a lot right now, and it's almost impossible for borrowers in that situation to sell or refinance without having thousands of dollars in cash to make up the difference.

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