A few years ago I started helping out making user generated content for a HL2 mod in my spare time.
The mod got quite popular and a couple of us got invited on an all expenses trip to the US to visit Valve's HQ and meet Gabe etc along with the mod's creator.
Helped re-write the entire thing from scratch to eliminate the myriad of bugs which had gradually crept into each subsequent update, still in my spare time.
A few months later started selling the mod on Steam.
I think so far it's sold in excess of 500k copies.
In case you haven't guessed, the game was Garry's mod.
I didn't make anywhere near as much as Garry the mods original author, who's pretty much set up his own fully funded game dev studio with the proceeds, but it was a fun summer nonetheless.
The mod got quite popular and a couple of us got invited on an all expenses trip to the US to visit Valve's HQ and meet Gabe etc along with the mod's creator.
Helped re-write the entire thing from scratch to eliminate the myriad of bugs which had gradually crept into each subsequent update, still in my spare time.
A few months later started selling the mod on Steam. I think so far it's sold in excess of 500k copies.
In case you haven't guessed, the game was Garry's mod.
I didn't make anywhere near as much as Garry the mods original author, who's pretty much set up his own fully funded game dev studio with the proceeds, but it was a fun summer nonetheless.