What is the cost of hosting a server on my computer?

I'll occasionally host a server on TF2 and Gmod for 2-3 friends of mine. Lately we've been playing Minecraft. This doesn't seem to be too hard on my connection, but everywhere I look, I see people paying a decent bit of money for a server. Does it cost anything to run the servers I run from time to time? Will it have any negative effects? Sorry for the dumb questions. I don't really know too much about this sort of thingWhat is the cost of hosting a server on my computer?
To host a good server, you'll need a business-class connection with a lot of bandwidth. A co-worker runs a TF2 server which is hosted in a data center, and it consumes about 2Mbit/s of bandwidth. This may not seem like much speed for a download, but it is quite a lot when it's continuous. You'll also probably want a static IP address, which costs extra from the ISP. If you don't plan to host a server 24/7, you could probably get away with using a residential connection, otherwise, it's probably just a good idea to use a colocation service to have a server you own put into a data center with a moderate-speed unmetered connection.What is the cost of hosting a server on my computer?
If you set them up on your own computer it shouldn't cost you a thing. but a good dedicated server isn't that expensive, and gets you way better results as they have a dedicated connection.