Hi jerry if you want to be an small itsp i can offer you this devices;
Cisco 805 Router
Quintum Tenor A400/800 (Analog)
For Server you can use a normal pc with Windows 2000 /xp professional or Windows 2000 Server Family
(if you know i offer you Linux.)
(For billing software i offer you Advanced Voip Billing System..
You can try this software online or download from http://www.advancedvoip.vom..Billing software requires MsSql or Oracle or MySql..) For purchasing this devices visit their web sites and find their resellers in your country..