Housing authorities may jointly exercise any or all of the powers conferred on such housing authorities, for the purpose of financing, planning, undertaking, constructing or operating a housing project or projects located within the “area of operation” of any one or more of such housing authorities; and may with respect to each other exercise any powers enumerated in “An Act in relation to aid of housing projects and cooperation with housing authorities and the Federal government by municipal corporations, political subdivisions and other public bodies of this State”, filed July 13, 1937, as amended, in addition to powers conferred by this Act.
     A housing authority may operate outside of its area of operation (1) by contract with another housing authority, or (2) by contract with a state public body not within the area of operation of another housing authority, if the Department shall first have found a shortage of safe or sanitary dwellings within the area of such State public body, in the manner provided by Section 3 of this Act, and shall have issued a certificate to this effect to such housing authority and to such State public body.