By most measures, mortgage rates fell to record lows this week - well below 4 percent for a 30 year fixed-rate mortgage. And while there are no indications that rates will go up significantly in the coming weeks, there's a good reason to get that mortgage sooner than later.

Here's why: To help pay for the now-approved payroll tax cut extension the Federal Housing Finance Agency will increase the guarantee fees (aka "g-fees") that are attached to single-family mortgage backed securities by 10 basis points starting in April.

What does that mean to the average borrower? The Mortgage Bankers Association, which opposed the measure when it was up for debate in late December, said that on a $200,000 mortgage it could cost an additional $4,000 in fees over the life of the mortgage.