Multiplayer computer games -- whether they be massive multiplayer games like "World of Warcraft" or first person shooters like "Call of Duty" -- have become a multimillion dollar industry. These games require servers to host or house the various games that store and run the operations of the game while you play. You can learn to make money by hosting a PC game, but it can be challenging and you likely won't get rich unless a major company leases your services.
Decide on the type of server you want to use. You can use your computer as a server, but once you shut down the computer, no one can use it. A dedicated server is in use 24-7 and will be unavailable for your own personal use.
Find a game to host by contacting developers or programmers working on games. If you want to court a large company like Blizzard, then you need to have large servers that can host a large-scale game. If you plan on courting a small company, then you don't need such a large system.
Figure out how you plan to charge. If you are working with a large company, they will likely lease your servers for their game; that will be the primary source of revenue. If you host a small scale or even local game, then you can charge people a monthly fee to play.
Create your pay-for-access system by working with your Internet service provider or hosting company. They both have the ability to set up a username and password system for either a membership section of your website, which you can provide access to your server, or directly with the server itself for a limited time. This will give only paying customers access to the server and the game.
Publicise your gaming space. If you are hosting a local game, then you will need to publicise your business in order to get people to come and play the game. The most common ways of publicising products are advertising, social media and news coverage.
Upgrade the servers when needed. If you want to continue making money, then you will need to upgrade your servers when the number of people gets too large or the games take up too much memory on the server.