California Code, Civil Code - CIV § 1917.616

A shared appreciation loan for seniors which bears a fixed interest rate complying with the usury provisions of Article XV of the California Constitution shall not be deemed to become usurious by reason of the payment of actual contingent interest pursuant to this chapter;  provided, however, that in no event may the amount of actual contingent interest received by the lender, plus the stated interest received by the lender, result in an annual percentage rate in excess of 1.5 times the applicable usury rate calculated pursuant to Article XV of the California Constitution, when all of such interest is applied over the actual term of the loan.