As the original link has been taken down and your advice is still very valid just one point I wanted to add: This is valid UNLESS it’s from someone whom you know well enough that they tell you the truth and knows what they are doing - in that case it can be a good idea to buy a used printer from someone who knows what they are doing and who has ironed out the teething problems some machines have and can provide advice if something goes wrong.

I was luckily enough to do something similar (with my CNC-machine,though. Standard MPCNC,but the friend I got them from is a pro - he designs his own mainboards and stuff - and would have been able to fix some issues myself without him/would have become frustrated) once and was able to help out a friend this way - he got a nice, highly modified but working very well Anycubic (back then one of the most reliable models…) and I got money for the next machine.

Otherwise: your advice is very valid. I also fucked up in that regard once.