HELP needed::Prepaid calling card

Dear forum members and visitors,
I’m interested in setting up an ITSP based on prepaid calling cards. For the begining, this project would include only two cities, that is one VoIP gateway will be installed in each city. Regarding my issue, I have several questions that I would like to be answered:
1. What minimum hardware and software will I need for this project? (2 VoIP gateways, what else?).
2. What hardware or software do I need to implement the IVR(Interactive Voice Response) service?
3. What hardware or software do I need to implement the Billing System? (account management, new acc. registration, etc.)
4. Is it possible to get this project implemented for $2000-$2500?

Your comments are highly appreciated!

Best Regards,
Tigran
worktravelusa@netsys.am