I've bought several dozen used S17 series machines (S17Pro, S17e) and I've had around a 30% success rate. The most common problem I've experienced with these is board failures. A machine that claims around 60T, when running with one board off will only give you 40T. As long as you know that going into the purchase, these machines are far less expensive than the current generation machines (S19 & T19).
All of that to say, S17s are notorious for board failures and low durability, so you’ll want to look at other models if you want a reliable machine.