Around here, there aren't that many nice trailer parks. The ones full of trailers that are for rent seem to be the lowest quality.
Then you have the places where someone rents out spaces, and people own thier own trailer, thats a step up, because as usual, there is ownership and people tend to take better care of thier own possessions than rented stuff.
However, sometimes you'll see a trailer on its own piece of land, not in a trailer park. Those are usually the nicest, because they also usually own the land.
Of course you can almost stratitfy thier income in those levels too, going from lowest to highest.