If you have a small business that sells at craft shows or other mobile markets, you can increase your earning potential by accepting credit card payments. This is particularly true if you sell higher-priced items, as your potential customers may not carry enough cash to pay for them. Square offers a mobile credit card reader that allows you to accept credit card payment easily. All you need to do is to download the Square app onto your smartphone or tablet, plug the card reader into your device, and accept card payments. Both the card reader and the app are free, but you have to pay a transaction fee per swipe.