The adjustable rate mortgage (ARM) is often a bargain. So are the 30-year, fixed-rate loans under 10 percent.

Some important details you should know about your ARM selection are:

• How often will it adjust?
• What is your index? The index is the identified base used to set your rate every time it adjusts - for example, a one-year treasury security for a one-year ARM.
• What is your margin? Margin is the spread between the index and your new rate at the time of adjustment.
• What are your caps? Caps are the maximum adjustments allowed, both short-term and for the life of the mortgage loan.