Getting a Low Mortgage Interest Rate: Rates Are at Historic Lows. Here's How to Qualify for One

The average mortgage interest rate on a 30-year fixed-rate loan fell to 4.85 percent in the last week in March. That's down from 4.98 percent just the week before.

The rate is also the lowest its been since government-backed mortgage financing company Freddie Mac has been recording it. Remember, Freddie Mac has been recording this rate since 1971, so last week's numbers truly were historic.

Not Everyone Qualifies for the Best Rates

These low interest rates combined with falling housing prices -- not to mention desperate sellers willing to make deals and a high inventory of available homes -- make this a great time to buy a house, especially for those homebuyers who don't have a residence of their own to sell first.

Unfortunately, not every borrower qualifies for the best mortgage interest rates. Those rates are reserved for those borrowers that mortgage lenders -- and the big three credit bureaus -- consider most trustworthy.

In other words, only those borrowers who lenders think will make their mortgage payments on time qualify for the top interest rates. Those who don't -- often called subprime borrowers or A- (or lower) borrowers -- get higher interest rates to make up for the extra risk lenders and banks take on when lending them money.

Nabbing the Top Mortgage Interest Rates

The best way for borrowers to qualify for the lowest mortgage interest rates is for them to approach mortgage lenders only when they are certain their credit scores are high enough.

Three companies issue credit scores to borrowers: Equifax, Experian and TransUnion. These three bodies track how strict borrowers are about paying their bills on time. They also track borrowers' debt levels and how much available credit they have.

They then issue credit scores. An excellent credit -- or FICO score -- is anything over 750.

Borrowers, then, should make sure they pay their credit card bills on time, that they don't fall behind on their car payments and that they don't generate too much debt. Borrowers who don't will find that their credit scores are too low, and that the historically low mortgage interest rates are out of their reach.

Borrowers can find their own credit score by visiting AnnualCreditReport.com. This service, sponsored by TransUnion, Experian and Equifax, allows borrowrs to obtain a free credit report from the three credit-reporting companies once every year.

Borrowers whose credit scores are low have two options: They can either apply for a loan anyway and accept that they may qualify for a higher mortgage interest rate, or they can wait, take the steps to repair their credit and then apply for a mortgage loan once their scores are higher.