What distances are you traveling? How much are you willing to rough it? How many band members are there?
Edit: I see four people and a trailer now. A travel trailer is probably not a good solution since you may not be able to double tow everywhere. (end edit)
If you're frequently going relatively long distances, an inexpensive motel room and a hatchback or minivan may end up being similar in cost to an RV (due mainly to getting much better gas milage), particularly if you plan on camping in nice campgrounds with full hookups. You can spend quite a few nights in a motel for $4000.
That said, if you have a tow vehicle, a smallish trailer as mentioned would be a reasonable option. If you don't have a suitable vehicle, perhaps look for a full-size passenger van in your budget. You could remove some of the seats and have room for a few air mattresses. Vans can make pretty good tow vehicles, too, so you could later get a travel trailer when your fortunes improve. (It would be worthwhile to keep that in mind when shopping, of course, and look for one with a hitch and a decent tow rating.)
