You will not pay tax twice. You will only pay tax where you register the car. (your home address on your ID)
For example, if you buy a Z in Cali, you will only pay the price of the car + title + fees (if there are any). Your home address on your drivers license will prove you do not live in Cali, there for they cant charge you state or city tax.
Once you bring the car home, you will take it to the MVD where they will make you pay tax + registration.
The only problem you may have, is acquiring a temp tag to get the car home, if you plan to drive it home. The best way to do this is to use the internet at the dealership and log on to your states MVD website and print a temp tag to drive home on. Option B would be to have the car shipped home but thats like four to seven hundred dollars.
Good luck, Im in the same boat as you so I know how it is, all the good Z's are in cali, and im further away in Phoenix!
