An authorized main residential structure in a conditional use manufactured home park may be a manufactured home or an authorized manufactured home. An authorized manufactured home, in addition to a manufactured home, is a housing unit manufactured off-site in one or more component parts or sections over 450 square feet in size, constructed to be connected to utilities; such dwellings are constructed to be towed on a chassis and may be placed upon a permanent or temporary foundation upon a lot or site in a manufactured home park or may remain supported by the chassis used for transportation, for year-round occupancy on a lot or site in a manufactured home park. Authorized manufactured homes can consist of one or more components for movement purposes and they may be capable of being joined together into one integral unit. This subsection, effective December 17, 1996, shall only apply to sites that have not been issued a placement permit prior to the effective date of this subsection.