It is hereby declared to be the policy of this state 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 dwelling accommodations at the lowest possible rates consistent with its providing decent, safe and sanitary dwelling accommodations, and that no housing authority shall construct or operate any such project for profit, or as a source of revenue to the city or the county. To this end an authority shall fix the rentals for dwellings in its projects at no higher rates than it shall find to be 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 the bonds of the authority; (b) to meet the cost of, and to provide for, maintaining and operating the projects (including the cost of any insurance) and the administrative expenses of the authority; and (c) to create (during not less than six (6) years immediately succeeding its issuance of any bonds) a reserve sufficient to meet the largest principal and interest payments which will be due on such bonds in any one year thereafter and to maintain such reserve.