Any municipality in acquiring an existing waterworks system may provide that payment therefor shall be made by issuing revenue bonds and delivering the same at such prices as may be agreed upon within the limitations prescribed in section five hereof. Any revenue bonds so issued in payment for an existing waterworks system shall for all purposes be regarded as partaking of the nature of and as being secured by a purchase money mortgage upon the property so acquired; and the holders thereof shall have, in addition to any other remedies and rights prescribed by this article, remedies and rights as may now or hereafter exist in law in the case of purchase money mortgages.