2. The provisions of subdivision one of this section shall not apply to a corporation, the principal asset of which shall be the ownership of a one or two family dwelling, where it appears either that the said corporation was organized and created, or that the controlling interest therein was acquired, within a period of six months prior to the execution, by said corporation of a bond or note evidencing indebtedness, and a mortgage creating a lien for said indebtedness on the said one or two family dwelling; provided, that as to any such bond, note or mortgage executed by such a corporation and effective prior to April sixth, nineteen hundred fifty-six, the defense of usury may be interposed only in an action or proceeding instituted for the collection, enforcement or foreclosure of such note, bond or mortgage. Any provision of any contract, or any separate written instrument executed prior to, simultaneously with or within sixty days after the delivery of any moneys to any borrower in connection with such indebtedness, whereby the defense of usury is waived or any such corporation is estopped from asserting it, is hereby declared to be contrary to public policy and absolutely void.