I got a refurbished Dell Optiplex 780 in 2014 and it still works pretty good.  Just getting too long in the tooth for modern usage.  But it was inexpensive and has given no trouble at all.  So far I feel exactly the same about the Optiplex 9020.  These are generally units that sat in giant offices where 200 people did insurance claims or processed financial transactions, that kind of thing.  The computer had been gone through carefully, cleaned, spruced up, and you get Windows 10 free.  I'm pretty happy.  Only complaint is the 3.0 USB port was damaged and failed about a month after I got it.  Still working on replacing it somehow.