may retain, for a term not to exceed twenty-five years from January 1, 1973, or for a term ending on the death of such owner or occupier, the right of use or occupancy of such property for any residential purpose which is not incompatible with the purposes of this subchapter or which does not impair the usefulness and attractiveness of the area designated for inclusion. Such owner or occupier must notify the Secretary of any intention to exercise such option within 60 days after receipt of the notice referred to in section 460x–10(c)(3) of this title. In situations where the United States has not heretofore acquired fee title to the improved property, the Secretary shall pay to the owner the value of the property on the date of such acquisition, less the value on such date of the right retained by the owner. In situations where the United States has heretofore acquired fee title to the improved property, the occupier may notify the Secretary that such occupier elects to retain continued use and occupancy of such property pursuant to this section, in which event the occupier shall pay to the Secretary the value of the additional right retained, which value shall be based upon the value of the property at the time of its acquisition by the Secretary.