If you decide to purchase an iPad and must purchase older, used iPad models, DO NOT look at anything older than a 2014 iPad Air 2 or 2015 iPad Mini 4.
Both of these models are the oldest iPad models that the up and coming iPadOS 14 will support, in the Fall of 2020.
If you must purchased used devices from unknown sources, you must ask more questions of the iOS device seller, ask for more photo/images, ask if the iPad has user/iCloud activation lock and ask for photos/images/short video proof, ANY REAL VISUAL PROOF, that such an iPad has been reset to factory settings and shown proof of the iOS device's start up screen showing the animated, moving, multi-language “Hello” Welcome to iPad screen.
If the iOS device seller is unwilling to do all of this to show you that the iPad, in question, is ready to use with no barriers to new user activation and use, pass on the iOS device and look at other iOS device sellers elsewhere.
Sorry & Best of Luck to You!