But if you're trying to source a 50-machine bulk order for a CS extracurricular program, with a uniform hardware profile so that students have a consistent experience, then no, you cannot reliably do that by going around to garage sales and rummaging through bargain bins. You cannot afford to repair all of these units (which WILL have a failure rate several times the average for a new machine) yourself. You can't even afford to troubleshoot them and manage the RMA process.