Oh… oh this CANNOT go well lol. In-world, I get the idea. Make use of the golden goose. Sure. But if someone is powerful enough to make a potion like that, it could EASILY backfire. Or worse, you could kill the dude and loose it all that way.
It’s ALWAYS easier to just bribe someone. Say “hey you like the pleasure district? Cool. I’ll hire anyone you want to be yours forever, while you live rent-free in my mansion, eating good for life. In trade, you become my potion maker.”… done. Guy is all yours, willing to work for you, might even make something BETTER than you planned because he’s comfy. Takes less effort, has a lower chance to backfire, and easier to sustain. Hell, have someone spy on him for the potions from time to time to learn how to do it if he gets cocky and you have to kick him out.