I assume you are talking about destination trailers and not park models… I know several that pull them around the country… depending how they are ordered they are just big travel trailers and fully self-contained… they are towables and legal everywhere without special permit…
They are nice trailers with 8 foot ceilings and plenty of room although not every park will have room for them…
Park models in my mind are 12 foot wide mini mobile homes, but even they and be ordered fully self contained… in some places a permit may be needed to move them…