It probably depends on what state you live in. In Colorado, you need 1) valid insurance and 2) a bill of sale. In that case you can drive home from the point of sale without tags and to the DMV as needed. The wording on the DMV website is a bit vague but it basically says that you can drive the car 'as needed' without tags for (IIRC) 3 days. That said, the dealer I bought from in RI offered to supply temporary RI tags but I had the car shipped so I didn't need them. I did pick up the car at the shipping company without any tags but I had all my purchase documentation and insurance information with me.