I've purchased 3 used Roombas, a Dirt Dog, and 2 used Scoobas off Ebay
. The Roombas were functioning, and the Scoobas were bought as nonworking. The Scoobas were repaired and work just fine. One 560 Roomba is on its 4th year
of cleaning, and works great. Another 560 was working fine, but then got fried when I didn't know any better (before this forum) and left it on charge for a whole 8 days. I bought a new replacement from iRobot at a good discount. The 3rd one was a 535 that I bought for mom, and it was like new, but sold because the brushes did not turn. I turned the brushes by hand 100 times one way, and 100 times the opposite way and the Roomba has been working just fine for my mom. The Dirt Dog was used, but barely, and looked brand new. That works great too. I also bought 2 used Metapo Clean Mate QQ2 robots off Ebay
, both of which work just fine also. I highly recommend buying used.