Any owner or owners, including beneficial owners (hereinafter in this section referred to as "owner"), of improved property on the date of its acquisition by the Secretary may, as a condition to such acquisition, retain the right of use and occupancy of the improved property for noncommercial residential purposes for a term ending at the death of such owner, or the death of his spouse, or at the death of the survivor of either of them. The owner shall elect the term to be reserved. The Secretary shall pay to the owner the fair market value of the property on the date of such acquisition less the fair market value on such date of the right retained by the owner.