^^^^
When I needed to replace my K03, both JKM and Kev @ Revo advised me very strongly to avoid secondhand turbo's unless I knew the history regarding mileage and type of driver usage.
Turbo's can be refurbished by a dedicated specialist and then supplied with a new warranty, but it still costs money and can cost about £200 just to have a turbo's condition properly assessed as worth repairing.