For the purposes of this subchapter, the term:
(1) “Commission” means the Mayor’s Official Residence Commission established pursuant to this subchapter.
(2) “Official residence” means the land and improvements where the Mayor has the exclusive right to live during the Mayor’s term of office, and which shall be exempt from property taxes.
(3) “Substantial nongovernment in-kind contributions” means any service reasonably valued at more than $5,000 which is received from any source other than the District government.