Hello Rodd,
Exhaust systems rust from the inside out. A seemingly solid used exhaust system may have a very short life. I am not trying to mess up anybody's sale, but I would save up a few more dollars and buy a new stainless also. Another concern would be if the used system was correctly fitted before welding during the original installation. You may be buying someone's squeeks and rattles.
Joe Alexander
Blacklick, Ohio