Becoming a VoIP Provider?

HI In my country there is not any VoIP provider, so i want to be the first one who will offer these services. But Im not informed about how VoIP works.My idea is to offer numbers for people, so they will be able to call from anywhere, in my country. I question is: what do i need for this, what tools do i need, how much would it cost to offer VoIP services in a territory of 10000 km(power,2)... Hope you'll understand my question... Thnx