Need 24-36 5th wheels a year-New or quality used...

RVs are really not designed for longer term living like you described, although some do live in them. Manufactured housing might be a better option, a basic single wide like this costs about the same as a basic 5th wheel RV, has twice the square footage, and meets residential energy codes (easier to heat and cool). Moving and setup costs would be higher, of course. For this many units on a site, you're looking at significant costs for installation of utilities, etc.