Unity Multiplayer P2P, Client-hosted game solution in unity?

We've been looking into creating a multiplayer game. We've made a few single player games, and there's not much that we haven't been able to figure out how to do.

But how on earth does multiplayer work?

There's a ton of documentation on Photon and we've gotten some simple things to work with it. But we're looking into P2P type multiplayer? We can't afford to keep servers running for a game that no one might play.

Other Unity games like "The Forest" seem to have gotten this down, but where can we find documentation on how this sort of system works?

 

If the game is not being played by anyone, you won't run a lot of servers. That's the idea of Photon's pricing being based on CCU (concurrent users). You can develop with the 20 CCU Free Subscription and once you want others to play it, buy a 100 CCU Subscription with a one-time payment. It's lasting 1 year in which you can figure out if players like the game...
Just saying.

The cheapest option for networking is to use Mirror or MLAPI (or others), create a game that is hosted by players and only run a service for the Matchmaking / NAT Punch Through.
This is not a secret. The forum is full of posts about all the options.

Have fun!