the biggest X factor is how to assess a mill if youre not local. In my case I called on the phone - even managed it on ebay- so I could get the details and a feel for the overall situation. The owners scared me away more than the mills. The one I ended up buying, the guy I could tell right away was an engineer and a straight shooter, knew his stuff and was friendly. From there you have to get a video of it starting up and running- just listen. That was my method. prior to finding my seller - I found a guy who could not take a video with his phone, not a good sign in 2019. one guy that would not cooperate with shipping "just come in a truck and get it". the cake taker was a guy on vaca in europe for a month but when he returned long after I had bought a mill he was non stop pestering me to buy one of his. With most big purchases I have found when you find the right one - you just know it.