It is hereby declared to be the policy of this Commonwealth that each housing authority shall manage and operate its housing projects in an efficient manner, so as to enable it to fix the rentals for dwellings at the lowest possible rates, consistent with providing decent, safe, and sanitary dwellings, and that no housing authority shall construct or operate any such project for profit. To this end an Authority shall fix rentals for dwellings in its projects at no higher rates than it shall find necessary, in order to produce revenues which, together with all other available moneys, revenues, income, and receipts of the Authority from whatever sources derived, will be sufficient--(a) to pay as the same become due the principal and interest on any bonds of the Authority; (b) to meet and provide for the cost of maintaining and operating of the projects (including the cost of any insurance) and the administrative expenses of the Authority; and (c) to create, during not less than the six years immediately succeeding its issuance of any bonds, a reserve sufficient to meet the largest principal interest payments which shall be due on such bonds in any one year thereafter, and to maintain such reserve; (d) to make such payments, if any, in lieu of taxes, as may be agreed upon pursuant to section twenty-three.¹