All cities not within a county, which now have or may hereafter have a population in excess of five hundred thousand inhabitants, may elect by the enactment of an ordinance by the legislative body of such city to have the collection of delinquent and back real estate taxes regulated and controlled by the provisions of sections 92.700 to 92.920 and to operate thereunder. The election to operate under the provisions of sections 92.700 to 92.920 may be rescinded by repealing said ordinance.