§ 6. Investment in obligations of housing corporations indirectly guaranteed pursuant to the "Servicemen's Readjustment Act of 1944". Subject to such regulations and restrictions as the superintendent of financial services finds to be necessary and proper, any bank, trust company or savings bank may invest in obligations of any corporation organized under any law of this state for the purpose of acquiring, constructing, owning, maintaining, operating, selling or conveying a housing project or projects (not including hotels but including accommodations for retail stores, shops, offices and other community services reasonably incident to such projects) located within this state, which obligations are (a) secured by a first mortgage lien on such project, or such part thereof, as was or is to be constructed or acquired out of the proceeds of such obligations, either directly or by issue under an indenture of mortgage from such corporation to a corporate trustee having its principal office in this state, and (b) guaranteed indirectly through the pledge as security therefor of obligations directly guaranteed under title three of an act of congress entitled the "Servicemen's Readjustment Act of 1944", in an aggregate amount equal to at least thirty per centum of the principal amount of all sums advanced to such corporation under the loan instrument or indenture during the period of construction and, upon completion, to the extent of at least forty per centum of the principal amount of such obligations.