The mortgagee shall pay to the Commissioner an initial MIP in an amount equal to one-half of one percent of the average outstanding principal obligation of the mortgage for the first year of amortization. After payment of the initial MIP, the mortgagee shall pay to the Commissioner an amount equal to one-half of one percent of the average outstanding principal obligation of the mortgage for the 12-month period preceding each subsequent anniversary date of the beginning of amortization.