The mortgage, to be eligible for insurance, shall be on property located in a state, as defined in §242.1. The mortgage shall cover real estate in which the mortgagor has one of the following interests:

(a) A fee simple title;

(b) A lease for not less than 99 years that is renewable; or

(c) A lease having a term of not less than 50 years to run from the date the mortgage is executed.