Used turbos are OK if they're the right size and have a known history or have been rebuilt. But honestly, the turbo is the "easy" part. They can be replaced so easily, grab one from ebay from a seller that has a good feedback rating and one that has detailed specifications, and you'll likely find lots for under $200.
The alternative is to get a small holset from a cummins diesel. You'll have to research, but they can be found for a good price.
Most "factory" turbos are very small, used to boost low torque motors up but not really generate huge power.
I've had great success with a cheap ebay turbo. When it dies, I'll replace it with another exactly the same unless I'm going for huge power / quicker spool.