[Dead_Meat]

Just make sure whatever you're driving across in is big enough.

Driving around in anything smaller than a mid-size SUV will be unbelievably uncomfortable, especially with all teh crap you'll take and the crap you'll pick up along the way.

There are speciality rentals that could maybe get you some kind of mobile home, which might even end up cheaper if you compare paying for a motel/hotel (and the hassle of finding one every night) than at least having teh option of pulling over and sleeping.

That said, mobile homes do around 10mpg, and it's a nifty 3000 mile trip you're considering, so bear the costs in mind. Fuel is, essentially, about 40% more expensive in the summer.