Except as provided in section 71-1561, no dealer shall sell, offer for sale, or lease in this state any new modular housing unit manufactured (1) more than six months after July 10, 1976, and before May 1, 1998, unless such modular housing unit meets or exceeds the standards established by the state agency responsible for regulation of modular housing units as such standards existed on the date of manufacture with respect to construction thereof and the installation of plumbing, heating, and electrical systems or (2) on or after May 1, 1998, unless such modular housing unit meets or exceeds the standards established by the commission with respect to construction thereof and the installation of plumbing, heating, and electrical systems.