How can i attract costumers back to my uncle's shop?

My uncle has a little supermarket in a pretty poor neighborhood where he sells affordable snacks, drinks, diapers, etc. He makes pretty good money off it for the past 35 years because of the lack of supermarkets in the area. Recently a new shop opened by some rich people pretty close and has been stealing all of his costumers. His shop is completely paid off, but he needs money for his house that's right next to ours. I reallly care about him and want to help him. Can you please give advice on how a small family owned business can win against a big supermarket like them?