a2 billing/moh

I’m new to free pbx and have a question. I’ve also had a2 billing installed and what not and here i can do what I’m trying to do. Your help would be greatly appreciated.
first: i want to be able to offer for sale calling cards on my website. Could you tell me how to do this? For your reference i have asterisk completely sip hosted on a remote dedicated server.
Second: i have a friend who wants to buy a pbx from me. Can i set him up with a pbx (either with my own personal invoicing software and give him login information to “his” section of freepbx, or can a2 billing handle this)?
Third of all: not really a2 billing but is there a way to upload music to for say
or something to get this music in the “default” category? I want to use ftp and upload some files.
Sorry for the new user questions, however your help would be greatly appreciated.
Yours sincerely
Michael Babcock