If you buy a car (and I don't know if this is a good idea, though I was tempted in Oz) be sure to buy a good one. New car dealerships tend to resell the best of the used trade ins they get and let the crummy ones go to the secondary lots that only sell used cars.

Used cars in the US do not have mandated quality inspections like I believe NZ does. Some states have a safety inspection but it is very superficial. Most deals are "as is" and buyer beware. You can get warranty but it's really just an insurance policy rather than the commitment of the dealership to stand behind it. It doesn't mean you aren't getting a lemon, it just works the odds that maybe it is not a lemon. Rental car companies sell their cars every few years. Maybe this is a good route. I guess they have had minimal maintenance. You can sell a used car fairly quickly at Car Max. It might be worth giving them a call to discover what their top sellers are, I'm guessing those would be the cars you could get the most for. Try the PR dept. if you can't find anyone who'll talk to you.

Don't buy a used car outside of a major market and be sure to sell there too. My experience with Durango vs LA suggests that in more rural locations the cars are generally driven to death and, because of that, no one will pay decent money for the sort of good used car you can easily find in LA because they aren't used to seeing good used cars. I have recommended going to Denver or Phoenix to buy a car to many friends in Durango and no one has ever been disappointed.

Buying a new car seems crazy but my cousin used to work for VW in England and they calculated that the two moments when you could get the best value per mile was at 3 months and 3 years. VW gave him a deal on their cars so he turned his cars over every 3 months because that was the moment he could get the most on the used market ... in England.

Personally I have had better luck hopping into areas, driving around, and then flying on to the next area either from where I flew in or out of an airport that was in the vicinity of the area I was exploring. That said most of my experience doing that was in NZ and Oz where one-way flights were easy to get and not too expensive ... not like the US.

Good luck and keep me informed!