Buying a Car Out of State

I live in New York state and my son is out in California.  We are interested in
my son acting as our agent in CA so we can buy a hopefully rust free car in
southern California which he would drive back to upstate NY.  My question is
how to handle the paper work.  If he buys and registers it in CA, we get to
pay CA sales tax and then pay NY sales tax when we transfer to our
ownership. Is there a way to register it here and send him the registration
and plates or to get a temporary registration he can use to transport the car
to here?  Thanks, Russell