Can literally grow all the money he could ever need...opens up shop as a merchant
WHY?!?!?
I mean, on one hand, if you just say f*** the world economy and grow your own money then you can wander and just be a forever rich tourist, and if they change the money you just get some of the new stuff and grow more again, maybe with some mountain villa where you grow more money just in case.
On the other hand if you are worried about the world economy, then just run away to some other country (so the king can't do anything to you) and mass produce potions, you buy some fields to grow your "materials" and just sell off the finished potions to adventurers mercs and soldiers, as long as you don't flood the market with ultra high tier pots it should be fine, and the more fighters who don't die because of your pots it will further invigorate the economy between whatever they salvage from monsters and find in dungeons to sell and what all they have to buy to keep living
either way, why choose to become a merchant in a medieval world setting? it's not a glamorous lifestyle, and unlike farming, where people are likely to appreciate the figurative (or literal) fruits of your labor once they get past the annoyance of actually having to pay you (unless the local lord is an ass and requisitions your food and you just get little or outright nothing for it), people mostly dislike merchants cause either you are a crap merchant and never can afford anything good to sell them, you are a "good merchant" and everyone hates you cause while you do have good stuff you make them pay more than they want to for your goods, or you are a rip off merchant and WAY overprice stuff and force people into making purchases...plus wandering merchants don't have citizenship which means you have to pay to enter a city, pay to sell your stuff, pay again to LEAVE the city in most places, and either wander alone through the dangers of the roads between or pay yet again to have people tag along and protect you, and the cycle is almost impossible to break, which means once you start you are almost certain to be stuck on that path for life
ok sure MC has cheat power, but still, that just means he can get more stock for his initial investment, he still has to sell it all, and he hasn't been shown to have combat OP-ness so unless he wants the OTHER merchants killing him off or worse, he can't just go undercutting everyone else's prices with infinite stock...unless he's actually going the f*** the economy route and he's just a freak who'd rather pretend play at being a merchant than just relax, and even then he'll still eventually need some means to protect himself once he's pissed off enough other merchants
and lastly, his cheat power is actually kinda low tier cheat power, unless there's more aspects down the line, he doesn't get OP fighting power so he can't even protect himself effectively, as far as has been shown he can't even magic magics aside from his crappy cultivate skill, and he can't even grow something unless he can get his hands on at least one of it in the first place, so no easy mass produced legendary weapons/armors/etc. rare ores and gems would be feasible since he can grow money, but the really good stuff usually can't be bought and thus he can't just grow them for instant OP up...although he should never starve or be without healy pots so that's a plus