The real property to be purchased by the borrower on a mortgage loan pursuant to this part shall be an owner-occupied housing unit, the acquisition price of which does not exceed 90 percent of the average purchase price in the statistical area, except that such acquisition cost shall not exceed 110 percent of the average purchase price in a targeted area. The average purchase price means the purchase price determined by the agency, through action of the policy committee, for similar owner-occupied units. Such determinations shall be made not less often than annually for each statistical area and targeted area.