I want to buy a second hand iPad and wonder what the oldest (meaning lowest costing) one worth getting? I know Apple as well as the app-makers lock constantly people out because their device is too old to run the latest iOS (this happens to me all the time with my 4th generation iPod Touch, which by the way is still going strong!). The bottom line: I don't want to pay more than necessary (I don't need a super high-resolution display or the "pro" pen feature) but also don't want to run into "needs iOS xxx which won't run on this iPad). I'll be using it mostly for reading stuff (eBooks, PDFs etc.) but also different apps of course. Another thing: is there a feature comparison/overview of all the different iPads available somewhere?