(a) In addition to payments otherwise authorized by this chapter, the agency shall make an additional payment not in excess of the amount provided by the applicable laws of the United States, or where no such laws are applicable, as shall be prescribed by regulation, to any displaced person who is displaced from a dwelling actually owned and occupied by the displaced person for not less than 180 days prior to the initiation of negotiations for the acquisition of the property. The additional payment shall include the following elements:
(1) the amount, if any, which when added to the acquisition cost of the dwelling acquired, equals the reasonable cost of a comparable dwelling.
(2) the amount, if any, which will compensate the displaced person for any increased interest costs which the person is required to pay for financing the acquisition of a comparable replacement dwelling. The amount shall be paid only if the dwelling acquired was encumbered by a bona fide mortgage which was a valid lien on the dwelling for not less than 180 days prior to the initiation of negotiations for the acquisition of the dwelling; and
(3) reasonable expenses incurred by the displaced person for evidence of title, recording fees, and other closing costs incident to the purchase of the replacement dwelling, but not including prepaid expenses.
(b) The additional payment authorized by this section 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 the date on which he receives final payment of all costs of the acquired dwelling, or the date on which 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 one year of such date.