In order to encourage and facilitate the construction or rehabilitation of housing to meet the needs of displaced persons who are displaced from dwellings because of any Federal or Federal financially assisted project, the head of the Federal agency administering such project is authorized to make loans as a part of the cost of any such project, or to approve loans as a part of the cost of any such project receiving Federal financial assistance, to nonprofit, limited dividend, or cooperative organizations or to public bodies, for necessary and reasonable expenses, prior to construction, for planning and obtaining federally insured mortgage financing for the rehabilitation or construction of housing for such displaced persons. Notwithstanding the preceding sentence, or any other law, such loans shall be available for not to exceed 80 per centum of the reasonable costs expected to be incurred in planning, and in obtaining financing for, such housing, prior to the availability of such financing, including, but not limited to, preliminary surveys and analyses of market needs, preliminary site engineering, preliminary architectural fees, site