All laborers and mechanics employed by contractors or subcontractors in housing or development activities assisted under this section shall be paid wages at rates not less than those prevailing on similar work in the locality as determined by the Secretary of Labor in accordance with sections
3141–3144,
3146, and
3147 of title
40: Provided, That this section shall apply to the construction of residential property only if such property is designed for residential use for eight or more families. No assistance shall be extended under this section with respect to any development activities without first obtaining adequate assurance that these labor standards will be maintained upon the work involved in such activities. The Secretary of Labor shall have, with respect to the labor standards specified in this subsection, the authority and functions set forth in Reorganization Plan Numbered 14 of 1950 (
64 Stat. 1267), and section
3145 of title
40.