Finally figured it out after thinking about it for awhile.
So what we have is uncle and father run competing shops, father disappears leaving daughter to struggle with running the place. Everyone is an idiot so no one thinks of MCs idea, the only ideas thought of are abandon the business or purchase the business. Daughter refuses to abandon the business, and Uncle can't purchase the shop due to guild rules but it really doesn't make sense why he specifically can't purchase it while it was his brothers shop.
I does feel like they're glossing over him being just a horrible person and driving his niece and mom into bankruptcy rather than try to help, but I guess the idea is if they go out of business quickly then he can just swoop in and solve everything with money? Either way it feels like the author just kind of wanted to abandon this problem cause we're definitely glossing over a lot of BS the uncle did.