If it's a Verizon phone it can be put on a Verizon account. All he has to do is call Verizon, tell them that he got a new phone he wants to switch his account to (or add to his account, whatever he wants to do) and give them the ESN of the phone. All he needs is his phone number and the ESN and they'll take care of the rest. Any Verizon store or customer service on the phone can do it.
Yes, but most smartphones can't be used on a verizon prepaid plan. Like you go pay 50 for a card for the month etc. I wasn't sure if this was one of them, but it's pretty limited selection. People have talked about needing to 'flash' most droids.