No cars while in training for student sailors, there isn't room on the base up there. He can come home on leave and pick up his car after he is done with school. Anyway, he has to earn his liberty privileges first, he'll be spending a LOT of time on base initially. He can't even wear civilian clothes right away.
He can have his laptop, cell and so on. I wouldn't recommend his TV and stereo until he is settled in. In school, they may change rooms/barracks and should be able to carry everything they own in one trip. Theft is also a problem, and he'll be sharing a room with several other guys. Best to wait until he knows the rules for his barracks, and how much room he will have.
Are you a member of the PreBUD/S Moms group? Here is the link:
Someone should have also started a group for your son's BUD/S class, too. There will be a list on the PreBUD/S page.