A shared appreciation mortgage or SAM is a mortgage in which the lender agrees as part of the loan to accept some or all payment in the form of a share of the increase in value (the appreciation) of the property.
Basically, the lender gives the buyer an unusually low-rate mortgage in return for a share (often 30%-50%) of the profit when the home is sold or transferred (often within a specified number of years).
Example: Suppose the current prevailing interest rate is 6%, and the property was purchased for $500,000. The borrower puts down $100,000 and takes out a mortgage of $400,000 amortized over 30 years. The lender and the borrower agree to a lower interest rate of 5%, and to a contingent interest of 20% of the appreciated value of the property. Because of the lower interest rate, the monthly payment is reduced from $2,398 to $2,147. However, this saving in monthly payments comes with a trade-off. Suppose the property is later sold for $700,000. Because of the agreement on the contingent interest, the borrower must pay the lender 20% of the profit, namely, $40,000.
By participating in the appreciation of the property, the lender takes an additional risk that is related to its value. Hence, whether this is a favorable trade-off depends on the conditions of the housing market. A shared appreciation mortgage differs from an equity-sharing agreement in that the principal of the loan is an unconditional obligation (to the extent collateralized by the property). Thus, if the property’s value decreases, the borrower would still owe whatever principal is outstanding, and if the borrower sells the property for a loss, the contingent interest is simply zero.