Renting an RV, while not cheap, is not a bank breaker either. This summer the wife and I rented a Large Class C from Cruise America (this unit would easily sleep all 5 of you). They had a 300 mile free discount online which helped with the costs. We didn't need any camping supplies/bedding/cooking stuff (as I had all those items already). But I would imagine you would require some stuff which can also be rented from them.
Not counting the $500.00 refundable deposit (which is put down before you leave and get back as long as you don't blow the rig up), we were out $305 and change for 4 days. That charge did included them doing the waste Dump and Propane refill (additional, or you can go find a propane place and sewer dump yourself).
We are in Phoenix, which too is pretty much central to what you are wanting to do. (Grand Canyon and New Mexico). If you decide to do this, I would get on Google Maps (or any other mapping program) and determine your mileage. Most RV rental places charge a mileage fee (usually 0.25$ per mile which is why the 300 free miles really helped out) so if you are planning on a long circular route (Phx - Grand Canyon - New Mexico - Phx) figuring out approx how far you are going to be going will help you plan accordingly for the bill at the end.
The RV was in great condition, clean inside, and the bed was actually not bad. The tires were new (or at least only had one or two trips on them), the stove, heater, water heater, and fridge worked with no problems.
Yes, it isn't going to be a poor man's getaway, but it IS a lot cheaper than renting on the east coast, driving out here, and driving back.
Just my 2 cents worth...your mileage may vary, see dealer for details.
