Subject to the availability of amounts approved in appropriations Acts, the Secretary shall, for approvable plans of action, provide to qualified purchasers assistance under section
1437f of title
42 sufficient to produce a gross income potential equal to the amount determined by multiplying 120 percent of the prevailing rents in the relevant local market area in which the housing is located by the number of units in the project (according to appropriate unit sizes), and any other incentives authorized under section
4109
(b) of this title that would have been provided to a qualified purchaser under section
4110 of this title.