bloodroses :
Honestly, I don't know if I'd trust a 2nd-hand GPU that was used for mining since they're used 24/7 at 100% GPU usage.
Ethereum is memory-bound, it doesn't push GPUs anywhere near 100%. Even if it did, reasonably well cooled GPUs with a clean PSU should still last many years. I used my HD5770 for seven years and it was under load 24/7 for half of that time. Still worked fine by the time I decided to upgrade to a GTX1050.
Manufacturing defects notwithstanding, most GPUs will outlive their useful life when taken good care of.