Idk, I think right after the post apocalypse would be the best time for a shop to open up. If you think about it, so much has been destroyed. People are in panic and chaos. There's money to be made in chaos, people want to stock up on food, water, supplies to ensure their survival. Ontop of that, a lot of other merchants could have had their things destroyed, some of the big competition could be dead for all we know.
So opening up 7 months would sound a little genius if it was out of greed for gil, or charity or a mixture of both.