Huh?
It will charge your account the data ($30 every month) plus your minute plan, plus your text plan.
It will have your phone numbers' SIM card in it. You can take that SIM card out, and give the phone to whoever you want- Your phone number stays on the SIM card.
If you give the phone to someone/sell it, you probably want to cancel your data plan, or else they'll keep charging you.