1.Purchase older used machines before 2015 before all the EPA regulations took place .
2.Don't purchase without a thumb (unless its a VG purchase) like buying half an excavator.
3.Check drive motors oil for metal in oil,smell the oil,if it smells bad the drive could be going bad (drives $$$25-3000 ea) FYI: I change drive oil 80/90w with each engine oil change (less than qt in ea drive just to be safe as drives have no filter,pump or means to take out normal wear/dirt)
4.Try to purchase a one owner machine that has been well cared (dont be too concerned about hrs)
5.Join
https://www.heavyequipmentforums.com/ and then go to excavators they will have a choice of mini or weight class & learn
6. Just to make sure if buying used go to eBay put in model you are purchasing & see what parts popup ,tracks, sprockets,drive motors,etc.
7. Loose bucket pins are no problem, easy replacement at local machine shop