I feel like this could be a brilliant recurring NPC.

Joins the party initially when they're low level and down on their luck, just looking for some extra muscle for a job.

Has a few adventures with them and just when the party starts to get used to having him around and actually start to like and get to know him, he asks to be cashed out and takes his share of the loot to buy the plot of ground where he wants to farm.

But it doesn't end there.

Some time later, the party is in a bind and need a place to lie low, so it's off to John's farm. He's doing okay... modestly successful, having slightly more than he started with at the end of each season. Still having trouble with local ne'er-do-wells (which the party may help with) but his adventuring time has served him well in dealing with them.

They part ways wishing each other well.

Some time later, the big bad that the party was hiding from discovers that John had been sheltering them and razes the farm, John barely escaping with his life by hiding in his well. In the well he discovers a cavern passage leading to a significant ore deposit, so he gets out of the farming business and into the mining business. Still, he needs to have protection from big bad, someone to clear out nasty things from the cave, help him procure mining equipment from a nearby city, and make contact with both vendors and buyers. Enter the players. With their help, John successfully gets his mine going and starts to make profit and turn his fortunes, even helping to improve the town.

Turns out he's massively successful and it goes to his head. He becomes a sort of robber baron, basically owning the town and treating it as his own private labor pool. Wages are slim, conditions are harsh, and pollution from the smelting furnaces has poisoned the land. He's got no need for the party anymore, having hired a cutthroat mercenary company to protect his holdings and intimidate the townspeople. When the party returns after some far off adventure, the town is unrecognizable.

Of all people, it's the former big bad that reaches out to them: it would seem some sort of a greed demon has been behind things all along, first forming a pact with Big Bad but later abandoning him when he failed to kill John years ago. When John discovered the cave, the demon realized that the end of the ore vein, way down there, sealed off a portal to it's hellish domain. So the demon formed a pact with John, in the guise of some less evil entity, helping him succeed in his business venture at the expense of all else, knowing that as soon as the vein runs out, the portal will be opened.

From there it's up to the heroes to try to stop the demon (and John, and maybe the Big Bad, bent on revenge) or if they fail, dealing with the effects of the portal to hell opening beneath the town.