I've watch a couple of these shows on tv and on You Tube. Mostly its a tax and zoning dodge. If its got wheels, its a vehicle not a house mentality. Once the zoning boards catch up, they'll be singing a different story. Some set cargo containers on pillars/supports so they are not a "permanent structure" and they avoid property taxes and building codes on the structure. To be a "trailer" it is required to be built within certain dimensions and have certain lighting patterns (example: brake and marker)and/or reflective material. They are just playing with loop holes in the zoning laws.