Get a square. They sound like they would fit your business perfect. They plug in to your smart phone. You can swipe (or key in) the information, take a picture or type in the description of the item, and then have your customer sign. It'll send you and your customer a receipt. Terms are good too - 2.75% for swipe / 3.25 + .15 per transaction for keyed entries. No setup fee, no annual fee, etc. Money posted every 24 hours...Even for AMEX.
We love ours - cancelled our Chase Merchant Services after we got this...Works well..
www.squareup.com