An authority shall have power to issue bonds from time to time in its discretion, for any of its corporate purposes. An authority shall also have power to issue refunding bonds for the purpose of paying or retiring bonds previously issued by it. An authority may issue such types of bonds as it may determine, including (without limiting the generality of the foregoing) bonds on which the principal and interest are payable: (a) exclusively from the income and revenues of the housing project financed with the proceeds of such bonds; (b) exclusively from the income and revenues of certain designated housing projects whether or not they are financed in whole or in part with the proceeds of such bonds; or (c) from its revenues generally including a pledge of tax receipts paid to it by the municipality in which it is located pursuant to an agreement made pursuant to N.H. Rev. Stat. § 205:4-c or in any other lawful manner. All such bonds may be additionally secured by mortgages upon the property held or to be held by it, by a pledge of a grant of contributions from the federal government, the state, a municipality or municipalities included in its area of operations, or other source. In connection with the incurrence of any indebtedness, an authority may covenant that it shall not thereafter mortgage the whole or any specified part of its property, pledge the whole or any specified part of its revenues, or pledge the whole or any specified part of tax receipts paid to it as aforesaid. Neither the commissioners of an authority nor any person executing the bonds shall be liable personally on the bonds by reason of the issuance thereof. The bonds and other obligations of an authority (and such bonds and obligations shall so state on their face) shall not be a debt of the municipality, the state or any political subdivision thereof and neither the municipality, the state or any political subdivision thereof shall be liable thereon, nor in any event shall such bonds or obligations be payable out of any funds or properties other than those of said authority. The bonds shall not constitute an indebtedness within the meaning of any debt limitation or restriction. Bonds of an authority are declared to be issued for an essential public and governmental purpose and to be public instrumentalities and, together with interest thereon and income therefrom, shall be exempt from taxes.