A really important question about my multiplayer game

Hey, so i’m in the middle of making a multiplayer game and this just came to my mind. Let’s say I have a matchmaking system, how exactly does it work? I mean, do I need to pay someone to host the multiplayer or what? let’s say that matchmaking system works, how do I get it working on Steam, let’s say. What do I need to do to make it so that whenever you press play it finds you a match with other few people, and you can actually play with them?

Search the forums for Advanced Multiplayer Sessions plugin, Multiplayer Lobby or for steam integration. I’m not very knowledgeable on the subject myself, but I believe you will find some guidance for your undertaking.
Of course it would be crazy to pay to someone for hosting while you are still in development phase. That’s why I suggest you dig into those plugins and setups.