Question: Upgrading Mac Mini without Apple ID
I bought an Mac Mini at a garage sale and reformatted it back to factory settings. It runs great but now want to go up to the latest OS which it asks for all the time but it wants an Apple ID before I can do this. Can I upgrade it without an Apple ID? I am going to sell it at some point so I don't want to get an Apple ID because I want the new user to personalize it for themselves. I don't want to lock down an Apple ID for myself.
Anyway to do this? I want to go to High Sierra.
Mac mini, OS X Mountain Lion (10.8.5)