Do you mean people on the internet or people who go on the other computer?
1. When you set up a network between two computers (with file sharing enables) you are only sharing a shared folder with the other computer. So no they can't view your information.
2. If you share the folders with the other computer that have your banking details in then, obviously, the other computer will be able to see them.
3. If you use a wireless connection and only have a wep encrypted password, and you are sharing the folders that have your banking details in then, although highly unlikely, yes someone could hack into your internet connection and view those files.