Subject to the provisions of § 8-309(h)(2) of the Transportation Article, the additional payment authorized by § 12-202 of this subtitle shall be made only to a displaced person who purchases and occupies a replacement dwelling which is decent, safe, and sanitary, not later than the end of the one-year period beginning on:
(1) The date on which he receives from the displacing agency final payment of all costs of the acquired dwelling; or
(2) The date on which the displacing agency’s obligation under § 12-206(b)(3) of this subtitle is met, whichever is later, except that the displacing agency may extend such period for good cause. If such period is extended, the payment under this section shall be based on the costs of relocating the person to a comparable replacement dwelling within 1 year of such date.