I've seen a lot of articles and posts about artist's work being stolen and used/sold. There was a facebook page that was just selling stolen art printed posters or on T-shirts. A lot of people reported it and it still didnt get taken down for a few more months.

On the other hand with his art style i think there's several industries that could definitely be somewhere he can go to

• Trading card Games
• Board Games
• Video Games

I think he can probably start posting more of his art at more places to get some attention and maybe start up a patreon account.