I do some computer repair work on the side and it was always a hassle to require cash or check payments from people. Square allows me to accept any credit card for a flat 2.75% fee. No other fees!
The device that attached to my iPhone is free as is the app that runs it. It direct deposits the money to my back account the next day. These guys have it figured out. You don't even have to run a business! It works for individuals too.
I ordered one for myself and I am going to try it out. I can't complain for free!