With an Adjustable Rate Mortgage (ARM), the interest rate changes periodically, and payments go up or down accordingly. Rates are tied to an index that reflects the cost of money at any given point in time. Generally speaking, lenders charge a lower initial interest rate for the ARM than for the fixed rate mortgage. If you are expecting interest rates to decrease in the future, or if you are trying to maximize your purchase power today knowing your income will rise in the future, then this loan may be right for you. Adjustable rate loans are attractive for buyers who expect to be in the home for a short period of time.