I would repeat what ksg5000 said, in that at 500 mi per day, you are talking about 6 straight days of just driving, seeing nothing but roadside at 65 mph (or more). Then there is the mandatory 8 hours rest for the driver after every 10 hours of driving. It will have to be nearly all Interstate highway travel, which is by far not the most scenic.
This now reduces your available site seeing time to less than 8 days maximum.
I saw the term "very expensive" used to try to describe the cost, I would substitute the word "Extremely" for the word very.
I as well as the rest of the responders are not here to put out the flames of your desire, but really don't see your plan as very realistic, unless of course you can come up with another 14 days and make it a month trip.
Good luck with what ever you decide.
