I have a sister that would like to start selling items at craft shows. She would like to use an Ipad (either a full size, or a mini) to keep track of inventory, sales, and cost of materials. She would also like to use the Ipad to take credit card payments, most likely at shows that have limited web access. What Ipad would be the best choice? Has anybody here had any experience with using an Ipad for business? Please, any advice i could give her would be greatly appreciated.