not less than 90 percent of (i) the families receiving such rental assistance are families whose incomes do not exceed 60 percent of the median family income for the area, as determined by the Secretary with adjustments for smaller and larger families, (except that the Secretary may establish income ceilings higher or lower than 60 percent of the median for the area on the basis of the Secretary’s findings that such variations are necessary because of prevailing levels of construction cost or fair market rent, or unusually high or low family income) at the time of occupancy or at the time funds are invested, whichever is later, or (ii) the dwelling units assisted with such funds are occupied by families having such incomes; and

the remainder of (i) the families receiving such rental assistance are households that qualify as low-income families (other than families described in subparagraph (A)) at the time of occupancy or at the time funds are invested, whichever is later, or (ii) the dwelling units assisted with such funds are occupied by such households;