To the best of my knowledge, construction & office type trailers are not under the 'local' building, elec, fire & plumbing codes for the 'unit'. They do however here in NJ require permits. Building for anchoring, stairs/ramp; electric for power hookup, and plumbing IF there are any sanitary, or domestic water connections.
The range of 'trailers' I see varies from the 'McTrailer' to ocean cargo containers, and a lot in between.
