Except as provided in Chapter 19.10 of this code, it is unlawful for any person to occupy or use any mobile home or trailer in the city, except within a mobile home park; provided however, that the same may be parked and used outside of the mobile home park for a period not to exceed forty-eight hours continuous time for sleeping and housekeeping purposes. Commercially constructed mobile homes (trailers) may be used as a temporary contractor’s or watchman’s office, lunchroom, and/or drying and tool room on the job site while construction is in progress and/or a building permit is valid. Commercially constructed and custom designed mobile homes (trailers) may be utilized as temporary quarters for business concerns on a site proposed for a permanent structure and for which a building permit has been applied for or issued. (Prior code § 17.12.120.)