Swoop is the easiest way to set up a shop and sell things. It does other awesome stuff too like payments through SMS, and really easy online/offline purchasing. Best of all it's based in MN.
Throughout the last year I have worked with Swoop to revamp the entire app from an early MVP state. This has included the UI/UX, service design, creation of new features, and third party integrations. The app has grown from a small app to a full featured app with multiple types of items, and invoicing, lots of pick up options for customers and smart interactions and through SMS based bots.
Soon the app will grow to include automated pickup lockers, and advanced types of invoices.