In a 1930s "trailer coach" everything was built-in. Seating areas and kitchen facilities were stationary, as were sleeping accommodations. The "rig" might even include a heating unit or furnace.
Above we see a vintage trailer coach advert. Chicago's Kozy Coach Company was building an 8 by 16 footer in 1938. At the time, the typical unit did not have a bathroom. This feature would not appear until the early 1940s and did not become standard until the early 1950s.
Advert from http://www.allmanufacturedhomes.com (Atlas Mobile Home Museum)
The social upheaval of The Great Depression caused a marked shift in the American perception of a trailer coach. In the years before 1930, a mobile abode was seen as a symbol of leisure, prosperity and adventure.
As the economy worsened, thousands lost their jobs and began roaming the country, trailer coach in tow, seeking whatever work was available. Soon, these rigs, originally designed only for sporadic use, were having to provide accommodations year-round. They began to take on a shoddy and worn-out appearance.
Moreover, the first trailer parks, or "auto camps", had been established in bucolic surroundings, often near lakes or National Parks. A host of amenities were often provided. By the mid-1930s, such facilities were being hastily created on the outskirts of cities, where migrant residents were crowded together, in squalid conditions, with little or no services to speak of.