If you want something cheap and simple with basic inventory and barcode scanning check out the solution I developed,
www.USBSwiper.com. It works with PayPal, PayLeap, Group ISO, Stripe, and Authorize.Net. Depending on your monthly volume and avg. ticket price we can get you into a merchant account that would be the best as far as fees go.
We have lots of customers that use our stuff with PayPal and then combine that with the PayPal Here mobile app. They basically use the two as companion products and we've gotten lots of good feedback.
We also have lots of people using our hardware card reader only with Intuit Merchant Services within QuickBooks. You can use it with regular QB, too. You don't have to get the POS version.