With a 5/1 adjustable-rate mortgage (ARM), your interest rate is fixed, or remains the same, for the first five years. Then, it adjusts once a year. When these mortgages have a 30-year term, that means you will have a fixed interest rate for five years and an adjustable rate for the next 25 years. These loans are also known as 5/1 hybrid adjustable-rate mortgages.