24 C.F.R. § 290.37
For any mortgage that, at the time HUD offers the mortgage for sale without FHA mortgage insurance, is delinquent and secures a subsidized project or unsubsidized project that receives any of the forms of assistance enumerated in paragraphs (4)(i) to (4)(iv) of the “subsidized project” definition in § 290.3:
(a) The mortgage purchaser and its successors and assigns shall require the mortgagor to record a covenant running with the land as part of any loan restructuring or of a final compromise of the mortgage debt and shall include a covenant in any foreclosure deed executed in connection with the mortgage. The covenant shall continue in effect until the last federal project-based rental assistance contract expires by its own terms. The covenant shall provide that, except where otherwise approved by HUD, a project purchaser shall agree to assume the obligations of any outstanding:
(b) In the event of foreclosure of the mortgage sold by HUD, the mortgage purchaser and its successors and assigns:
[61 FR 11685, Mar. 21, 1996, as amended at 61 FR 32265, June 21, 1996]