A shared appreciation mortgage, comprising: a loan from a lender to a customer, secured by a mortgage, to purchase a property at a price, the loan containing a first loan and a second loan, where the first loan is a conventional principal and interest loan arrangement, and the second loan is a fixed interest rate loan where the interest rate is related to the rate of rental return from real estate properties of the value of the second loan; a residential purchase contract containing an obligation for the lender to pay to the customer an amount equal to the outstanding second loan immediately before the property is sold in order to purchase an interest in the property proportional to the value of the outstanding second loan relative to the purchase price of the property, so that the lender and customer jointly own the property at the time of sale; an obligation on the customer to repay the outstanding part of the first loan and the outstanding part of the second loan upon the sale of the property; wherein, the size of the second loan is periodically reviewed.