FAF funds may be used only to pay the development costs of dwelling units to the extent they are or would be chargeable for federal income tax purposes to the project's capital account with a proper election by a taxpayer. FAF funds may be used toward the development costs of mixed-income or mixed-use projects, if the costs: Would be properly includable in an FHA-insured mortgage loan insured under the National Housing Act, 12 U.S.C. §1715l(d)(4); and Are allocable to dwelling units to be occupied by very low-income households and facilities related and subordinate to a FHA insured mortgage loan under the National Housing Act, 12 U.S.C. §1715l(d)(4). Any allocation shall be made under §B(2) of this regulation on a basis that reasonably reflects the actual costs of the dwelling units to be occupied by very low-income households as a percentage of the overall development costs of such mixed-income or mixed-use project.