Wow, had no idea they were that expensive!
I plugged in Alabama for 2 weeks for a 25' rv and 3000 mi is over $2500 before insurance and all the extras.
If you can weasel out of sales tax on private party deals, maybe just buy a RV for the trip.
Quick CL search by me shows a bunch of nice condition low mile Cs for $10-15k and even the $10 k ones were really nice.
If you know what you're looking for, strike a deal on one. If you don't have the cash, you could probably turn it back around and sell it before you make the second payment.
Should be easy enough to find one that you can sell for what you bought it for or close to it.
That's what I did with my last camper and actually made about 3 grand on the deal, but I took it to AK for 2 years and then sold it up there before moving back. Wouldn't expect to turn much profit though in the same market you bought it in, but a couple weeks use and a couple thousand miles doesn't deprecate the RV. Plus you stand a good chance of scoring one all ready to go, fully stocked. That's how I bought and sold ours, pretty much ready to camp. I think that swayed the buyers (wife), since all it needed was food in the fridge and a tank of water.