Home Equity Conversion Mortgage (HECM) mortgagors may have only one principal residence at any one time.
Mortgagee Letter 09-11 is available at https://www.hud.gov/program_offices/administration/hudclips/letters/mortgagee
24 CFR 206.3 https://www.ecfr.gov/cgi-bin/text-idx?tpl=/ecfrbrowse/Title24/24cfr206_main_02.tpl