There is stuff that people in trailers need. Most of it is readily available but a some things are special. For example some one
The little 12 volt "acorn" light bulbs are more difficult to find. These are specific parts necessary for a trailer and only really used in trailers, as far as I can tell.
I've noticed that there are a lot of non-FEMA trailers set up around town. They are easy to spot because they are often old, they aren't white, aren't installed FEMA style or don't fit the profile. These people don't have anyone to call for service. They also need to be anchored to the ground with auger anchors and and metal straps, I had to go to an RV dealer to get the ones I needed.
There is a much larger range of' 'dual use' products, things which are helpful utilizing the limited space available in the trailer.