How cheap are 15-year fixed-rate mortgages today? The answer may surprise you.

The fact is, 15-year FRMs now cost less (in annual interest rates) than do 1-year adjustable rate mortgages. In other words, it's now truly cheaper to take out a mortgage guaranteed to not go up for the next 15 years, than it is to take out a mortgage that could spike through the ceiling as soon as 366 days from now.

What should you do with this information? Fool contributor Rich Smith explains. 

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