How to run a free game server?

Hi everyone,
I was looking to make a FPS with Unity 3.5 and I wanted to know if there was any way to run my own server (with second-hand computers) for free. I can’t pay $5000 for a server. PLZ HELP!!!
ANY HELP WILL BE HELPFUL
THX

Forward a port from your router to your computer, then use your local server e.g. 194.34.23.23:port to host your website

Do you just need hosting space? If so, I use Dreamhost (note: referral link) for hosting. $9 per month, unlimited domains. Can be a bit slow at peak times. Alternatively look at Amazon S3.

Of course, if you want a multiplayer server, and not just hosting space, you’re going to need a different solution. What exactly do you need? I highly doubt you’ll need to pay $5000 for a server.

I need any kind of software that I can run on some computers so i can have some multiplayer servers. oh and by the way it was electroserver that cost $5000 for unlimited CCU’s. And be sure that this software can run on Linux.