So I want to buy a used rx 570. The guy says he has used it for mining (I think about 7 months because that's how long ago he bought it) but he regularly cleaned it and he always ran it at a low temperature and fanspeed, because he didn't want to overload the card (and I'm guessing for efficiency purposes). Would buying yhis be a good and save purchase?
Depends on the price. It will have no warranty so factor that in. You should also ask if the BIOS was flashed with one specifically for mining, if it has flashing it back carries a risk of bricking the card.