We are planning a 21 day road trip around Nevada, California, Utah and Arizona. As we are under 21 we cannot hire a car so our only option is to buy a second hand one and sell it again at the next of the trip.
Take a look at https://dmvnv.com/nvregreq.htm
Can we buy a car in Nevada with a UK license?
Yes. Sellers don't care about your license, they just care about whether you can pay what they want
Do we have to register the car if we will only own it for 20 days?
Yes. A car must be registered and insured to be legally driven
Can we get insurance online and drive it the same day?
Maybe. You probably need to have the insurance worked out upfront and a good insurance broker may be able to handle the transaction in a single day.
If we do not need to register it, do we need any permits instead?
You need to register it.
Buying is easy, registering and insuring is hard. For registration you need a physical Nevada address and it's unclear (to me) whether you need a Nevada license or not. Covid further complicates matter: some DMV (Department of Motor Vehicles) locations may have restrictions, modified opening times, require appointments and/or are closed altogether and this can change on short notice.
