Stardew Valley. Runs on everything, not just "viable" OSs, made by a single person, and easily competes with an entire genre of gaming to pay the author.
The upper bound of building a business on top of Stardew Valley appears to be https://www.patreon.com/pathoschild which makes under $400 per month after Patreon's cut. That's not enough to work as a single person full time let alone hiring a team.
The upper bound of building a business on top of Stardew Valley appears to be https://www.patreon.com/pathoschild which makes under $400 per month after Patreon's cut. That's not enough to work as a single person full time let alone hiring a team.