(b) In the operation or management of housing projects an authority shall, at all times, rent or lease the dwelling accommodations therein at rentals within the financial reach of families of low income. The authority, subject to approval by the Commissioner of Housing, shall fix maximum income limits for the admission and for the continued occupancy of families in such housing, provided such maximum income limits and all revisions thereof for housing projects operated pursuant to any contract with any agency of the federal government shall be subject to the prior approval of such federal agency. The commissioner shall define the income of a family to provide the basis for determining eligibility for the admission and for the continued occupancy of families under the maximum income limits fixed and approved. The definition of family income by the commissioner may provide for the exclusion of all or part of the income of family members which, in the judgment of the commissioner, is not generally available to meet the cost of basic living needs of the family.