I have (had) 3 of the FolgerTech kit printers - the 2020 Prusa i3 (sold this one because I just didnt use it), the Kossel Rev B, and the large format FT-5 - each one has it's own challenges and quirks, but each one works decently when assembled well - ie: tight and square.
I also have two Solidoodle 4s purchased used and then upgraded.
personally, I would not buy from ebay or aliexpress - just my personal opinion, however.
SD4 #1 & #2 - Lawsy carriages, E3D v6, Rumba controller board, mirror bed plate, X motor fan, upgraded PSU & Mica bed heater
SD4 #3 - in the works ~ Folgertech FT-5, rev 1
Printit Industries Beta Tester - Horizon H1