Buying out-of-state

Yes, you pay California's 8.250% sales tax if you drive the car off the lot. If you have the car shipped to you, you don't pay California tax. You would pay the taxes when you register the car in your state. In Texas the sales tax is lower than in California. You need to check if your state would refund you any tax paid over the amount you would owe in your state. Most state would credit taxes already paid, I just don't know if they would be in the refund business. I bought my car from Dianne in California and had it shipped to Texas where I got a 30 day permit and then registered the car and paid the taxes all at once.

 

Also, they will provide you with a temp tag for a fee that will allow you to car the car back to your state. When I got the car delivered to my house it had no plates or temp tags. I got a 30 day temp for $25 that allow me to take the car on a road trip to Connecticut. I registered the car after I got back from the road trip.

 

Sounds like the previous poster is a good source. The (almost) only thing that I will add to that is that you should contact your local county tag office/tax assessor/etc...to find out what you have to do in Illinois for a car purchased out of state. One good thing is that since you're physically close to another state (Indiana, in your case) this isn't going to be a heavy lift. They do it every day, but that doesn't mean that they do it easy.
Every state is different....trust me!
32 years of military life speaking here. I've probably bought cars in 20 different states, and I've almost always registered them in another state.
Illinois is as broke as the Ten Commandments. They might just be one of those states that charge you their sales/property/road use/exise/whatever tax and let you figure out how to get your already paid sales tax back from Caly (another broke-a$$ state.)
I don't think that this will be the case though....and a few phone calls will clear things up before you get on the big white bird to the PRC.
http://www.cookcountyassessor.com/

One last thing.
This is presuming that you're traveling to/from Caly to get the car. Disregard otherwise. I get disregarded all the time.
You're probably already thinking along these lines, but make sure that you get a HARD quote before you book an airline---especially since it's going to be a one-way booking. Wear easy to get off shoes!---because you WILL get some TSA love on a one-way flight! I've bought several vehicles sight unseen before, and it's not that big a deal. Hopefully.....you'll have a purchase order in hand when the TSA is groping around (pun unintended) trying to determine whether or not you’re a threat to National Security.
As mentioned above, Dianne (Whitmore, IIRC) in California has done this before. Pop a flare over her account and see if she can beat the deal that you're negotiating in the Bay area. I'm a little skeptical of a dealership in SF area being the lowest cost place to buy a V, but hey....stranger things have happened.
If nothing else....she will be able to offer more knowledgeable advice on the whether or not the deal is worth traveling three time zones for!
I fibbed earlier.
There's one more one last thing.
Do a VERY detailed inspection on your new car before you sign on the dotted line! This is always important, but doubly so if you don't want to spot a shipping boo-boo when you're three states away and accelerating.
Good Luck!