I'm not sure what you are asking here.
I would think it would take as long as it takes you to sign them up for a line of service and then activate their device on your plan. 5-10 minutes if you already have a phone and a SIM card.
hcgames, we are here for you to help in any way possible! Can you please confirm if you are trying to add a line of service to your account? JoseL_VZW