Before initial endorsement of the mortgage for insurance, the mortgagor, the mortgagee, and HUD shall enter into an agreement in form and content satisfactory to HUD for the purpose of precluding any excess of mortgage proceeds over statutory limitations. Under this agreement, the mortgagor shall disclose its relationship with the builder, including any collateral agreement, and shall agree:
(a) To execute a Certificate of Actual Costs, upon completion of all physical improvements on the mortgaged property.
(b) To apply any cost savings in accordance with the provisions below.