The only condition guarantee you can reasonably expect is from getting them checked from a turbo specialist. At a look and a touch. How freely the wheels spin, is there any lateral freeplay in the wheels. Any undue marks or cuts on the blades. Oil leaks and general cleanliness can give an indication. Crud in the oil lines.. ... Second hand turbos are a gamble.
I'd look at the owner/seller - Do they wear nice clothes/have fancy watch/Money? Or another way to put it - why are they selling them? Would the seller flick them off without care for bigger/upgrade, or are they removed from a car due to tiredness? But in my opinion I suggest forking out for new...Used turbos are like getting a girlfriend wilted flowers.
Either that, or chuck a new seal kit through them to be sure. Cheap enough for a kit. $80 or there abouts...
