This is far and away the most popular type of mortgage given to borrowers today. Why? Because, as noted in our real estate definition for adjustable-rate mortgages, fixed-rate mortgages are the sameeach and every month of the amortization period. There is no potential fluctuation with interest rates, as there is with ARMs. So, as long as your clients lock into a low rate, they can more capably plan their finances around their consistent monthly payments to their lenders.