There are def pos system type apps in the App Store, apps that work with bar code scanners and credit card scanners and receipt printers over Bluetooth (although I highly suggest try to get the customer to let you email the receipt, it's green, costs you nothing, and you get to log an email address for future email marketing). The common Mac based one is Lightspeed although it is expensive and i think you need a mac to set it up/act as the server. I'm sure if you shop around you can find a great value on a pos type app. Go for the mini it's cheaper and smaller, the full size one is kinda hard to hold when running a buisness that requires showing products to people. Get the model that takes a SIM card so you'll have Internet everywhere, but make sure you get a good deal on a data plan, most usa data plans these days are highway robbery IMO. I think the best deals you can get on tablet data plans are when you tack them on to family plans. Even with the data plan try to be on wifi whenever possible. Oh and watch that ipad like a hawk when out in those farmers markets, even in the friendliest of environments the ipad is so coveted it has a way of making honest people dishonest.