A mortgage allows the potential homeowner the chance to spread the payments out over a period of several years. The average mortgage loan is 30 years. Obviously the number one reason for a mortgage is because the person buying the home does not have the money to pay cash and must borrow the money over time from a mortgage company which will be paid back with interest. Anyone having 100,000 dollars cash (median price for a house, depending on the location), would not need to borrow the money.