I made a trailer park in one of my CAW worlds. Here's a picture:
https://i.imgur.com/JNFomir.jpg
At the far left is the Ray of Sunshine Park, from the Town Life SP. Next to it is a 30x20 lot with a trailer. Along the road to the back are two 15x20 lots with trailers and a 9x20 lot with the trailer park office. Along the road to the front are a 20x30 lot and a 15x20 lot with trailers.
They are individual residential lots. You could make one similarly without using CAW, by placing the lots close together along both sides of a road, preferably near the end of a road to give it more of a trailer park look.
In my trailer park, I made the large one next to the playground and the small one to the front at the right. The Front left one is from Moonlight Falls, the one to the back next to the office is from Riverview, and the light green one I made by copying the pre-fabulous house in Sunset Valley, but putting it up on foundation squares to make it look more like a trailer. I added a second bedroom to it, and to the one from Riverview. The two I made also have two bedrooms each, but the one from Moonlight Falls has only one bedroom.