I'll tell you what I did. I had a gooseneck trailer with a decent tack room. I put insulation and paneling in the tack room along with a bed, curtains, TV microwave, drawers. Then I put electrical with a camper plug.
I made my own living quarters. When I got to a show, the back got scrubbed out and my working student/groom had a bunk in there. We stayed in it at all the horse shows so we could be with the horses early. It was very comfortable.
Event people are not known for being very snobby about being fancy. They are much more down to earth than my jumper folks. It wasn't uncommon to see any kind of tent/living arrangements at even the big events.