Prior to its approval of any redevelopment plan, the authority shall be satisfied that there is a feasible method for the temporary relocation of families to be displaced from the project area, and that there are available or will be provided, in the project area or in other areas not less desirable in regard to public utilities and public and commercial facilities and at rents or prices within the financial means of the families displaced from the project area, decent, safe, and sanitary dwellings equal in number to the number of the displaced families.