A year or so ago i flew to Las Vegas and hired a car and did a drive around several national parks/sites in Utah/Arizona, its in my trip reports below....
I'd drive often times at evening/night for 3 hours or so and leave the days to spend walking and seeing sites, hiking in national parks etc... I thought it worked out pretty well...
In April of this year i flew to Orlando and hired a 25ft RV/winnebago type motor home and drove across the US to LA, stopping in at Dallas, Las Vegas, New Orleans etc... Had it for $1 a night and they chucked in US$500 for fuel against receipts, no one way fee as it was relocating it... I rented it for a 11 days so was a bit of a whistle stop but some amazing viewing along the way... Could have had it for like 20 days or so but after 15 days at $1 a day it would have gone up to about $75 a day for the last 5 or so....
But no having to pay for accomodation, didn't even bother to stop at RV parks, just found places to park it in the cities or at car/truck stops along the way.... Was a bit of a gaz guzzler but i figured out getting in behind a semi trailer and driving a few hundred miles made the fuel consumption a lot better....
All up the whole thing in extra fuel above the US$500 included and a few other incidentals probably came to about US$300 or A$500 which isn't bad for a nearly 2 week holdiay... There was a mileage inclusion which was for a pretty straight route but about 32 cents for each mile after that, so an extra 900 miles taking less direct routes would be US$300???
Just some another option and some food for thought.... Not a top down, sporty Mustang convertible by any means...