Here is a simple store setup with a clerk to interact with. You will be prompted to either buy or sell. Once you have decided, either your inventory or the shop's will be visible. You will then have to type the appropriate words exactly as you read them in order for the clerk to find the items. Once done finding the items he will do the corresponding action with them.
This project is apart of a learning series for River Tech School. This project is an example of how inventories can work and how you may manipulate lists of objects.