I bought my Janome 300E used off of an ebay add but from a local person who dropped it off and it is working fine and I am very happy with the $600 I saved. I have since talked to other home embroidery people and find that many of them would like to upgrade their machine to a new model but the dealer either won't take a trade in or the trade in offer is too low. You may want to check with your local dealer if they know of anyone interested in selling a machine or if there is a local embroidery group, get the word out that you are looking.
Craigslist could be an option to look for people who are interested in selling their machine, which you could then see and try out locally and not blindly over the internet. You could also consider what we do with used car purchases, take it into a technicial to get it cheaned and serviced to have them kick the tires to see if it is working correctly.