A fixed mortgage is a property loan on which a homeowner pays the same amount every month - for the lifetime of the loan. This is usually for a loan with a lifetime of 15-30 years. The monthly payment covers accruing interest and a small amount of the principle. During the initial period - and throughout the loan - the interest is kept comparatively low. However, many loans only start with a fixed rate for the initial period, often 2-5 years, before it automatically switches to a variable rate mortgage, which can cause monthly payments to spike.