 The process of selling a loan from the mortgage bank to another investor is referred to as selling the loan on the secondary market.This is in contrast to the primary market, which for mortgages typically refers to the bank buying the mortgage deed of trust from the homeowner for the face amount of the loan, adjusted for discount points and other price adjustments.Mortgage banks sell the loans because the funds received pay down their warehouse lines of credit which enables the mortgage bank to continue to lend.