Adjustable Rate Mortgages (ARM)s are loans whose interest rate can vary during the loan's term. These loans usually have a fixed interest rate for an initial period of time and then can adjust based on current market conditions. The initial rate on an ARM is lower than on a fixed rate mortgage which allows you to afford and hence purchase a more expensive home. Adjustable rate mortgages are usually amortized over a period of 30 years with the initial rate being fixed for anywhere from 1 month to 10 years. All ARM loans have a "margin" plus an "index."
When the time comes for the ARM to adjust, the margin will be added to the index and typically rounded to the nearest 1/8 of one percent to arrive at the new interest rate. That rate will then be fixed for the next adjustment period. This adjustment can occur every year, but there are factors limiting how much the rates can adjust. These factors are called "caps".
