Not a limit on an RV, but sort of fits in there. At least in Arizona to have a 'temporary' structure - i.e. not a house - you must be less than 400 sq. ft. This way you don't pay property taxes on the unit. That is why all the park models are 399. They add on a 'Arizona room' which is a screened (or enclosed) porch. But it can't be attached. This way you can get more space with no more taxes.
I hope I have this all somewhat correct!
