Bonds issued under authority of sections 22a-500 to 22a-519, inclusive, shall be sold by the authority at public or private sale at a price determined by the issuer thereof. The bonds may bear a single or variable rate of interest and may bear different rates of interest for different maturities. The proceeds arising from the sale of any bonds issued under the authority of sections 22a-500 to 22a-519, inclusive, by an authority shall be kept in accounts separate from other funds of the authority and shall be expended only for the purposes and subject to the provisions of sections 22a-500 to 22a-519, inclusive.