Well first you need a computer. Then you need the server software. Then you configure the software and unblock the required ports. Then you run the software.
Go get a computer, put linux on it, install steamcmd, then install whatever games you want to run servers for. Tutorials and required specs for the game servers are just a google search away. I wouldnt do anything business related until you have at least run a game server that has a decent amount of users before you try to sell them. Its not like some basic cpanel webhosting setup thats for sure.
I agree, you should do some homework on the industry and try to find out exactly what it takes to operate a game server business. Its one thing to get the server online but a total different ball game when it comes to technical problems. So just do some research on the industry an try setting up your own game server like saschoen mentioned to familiarize yourself more.
1. (Dedicated) Servers
2. Control panel (Multicraft, Opengamepanel, TCAdmin etc.)
3. Billing and support system (WHMCS?) and a website for them
4. Linux knowledge as well as knowledge about the games you are going to host to provide support and set them up.