(a) No loan shall be made for financing except through a qualified mortgage lender.
(b) All mortgage loans made for financing pursuant to this chapter from the proceeds of bonds issued on or before October 1, 1983, shall be insured or guaranteed, in whole or in part, by any instrumentality of the United States, or the State of California, or by any person licensed to insure mortgages in this state. Mortgage loans made for financing pursuant to this chapter from the proceeds of bonds issued after October 1, 1983, may be insured or guaranteed, in whole or in part by those entities or persons. However, nothing in this subdivision shall impair any contractual rights which may have vested in bondholders or other persons prior to October 1, 1983.