Sales Tax - you pay the legal sales tax where you buy a vehicle, and if you register the vehicle in a different state - you owe tax there.
I grew up near the corner of Arkansas, Louisiana and Texas.
Vehicle dealers know the process intimately, and charged the proper sales tax on the invoice.
Bought new car in Texas once which was registered in Arkansas. They split out the amount of sales tax going to each state on the final sales papers.
Sales of used vehicles - the sales tax owed can depend upon the sale price, or upon the 'current value'. Texas is a state which has a 'current value' rule. Once gave a nine year old vehicle to my daughter, and she had to pay $62.50 because that is the 'minimum tax due' on a vehicle sale because their 'minimum sale or transfer' is 'valued' at $1,000.
Last research I have, and talking to my step-daughter in Portland is that Oregon has no sales tax/ collects no sales tax.
The real question is where are you going to register the vehicle? What is the tax there? I have no idea of rules to register a vehicle in CA. If a non-resident can even register a vehicle in the US.
Full-Time 2014 - ????
โNot all who wander are lost.โ
"You were supposed to turn back at the last street."
2012 Ram 2500 Mega Cab
2014 Flagstaff 832IKBS TT