I just have a TS server running on my computer. My bandwidth is enough for my coil group, and we are the only ones who use it. I'm sure that you could have up to about 20 people on before the connection starts to go to hell. my first fc had it hosted on our fc leaders pc, but we started running into issues when all 3 coil groups and a few extras were on at once.

So if your fc is rather small, you may not have to pay for one.