I bought an old 66 head, just the head, for a treadle. She is just Plain Jane, but she was packed like she was a prize machine and came in very good shape. Put her in the treadle and have used her various times when there are power failures that sometimes last as long as 12 days.
My big caution is thoroughly check the feedback of any seller.

I bought a featherweight for a good price and it was perfect!

Yes, I purchased my Bernina on eBay for $1400. It was in perfect condition from a person who owned a quilt shop and it was a store model. There was supposed to be something that hooks up to the Internet which she didn't have, it may have been an option she didn't purchase and I was fine with that. My experience was very good.

Any time I am tempted, I remember the sewing machine my sister ordered. The description said "runs good". Aside from the fact that it was poorly packaged and beat to pieces, there was no motor on it. I have bought from ebay when it was something like a sewing pattern, but for sewing machines, I buy from shopgoodwill and only when I can pick it up within reasonable driving distance.

I recently bought a MC14000 on Ebay. I saved more than half of the SALE price and 2/3 of the MSRP. Everything about the sale was excellent. I simply could not afford a machine like this from a local dealer nor could I buy it online from one of the excellent online sellers anywhere near the price. I have full warranty through Janome should I need it. I have a good relationship with a Janome technician for yearly service. I suggest that you click on the seller and investigate how long he/she has been selling on Ebay and read all of the reviews. You can ask questions if you need to through Ebay. I ditched one of my first selections because the answer the seller gave did not fit at all. I would not bid on anything with a seller with less than 50 sales on Ebay with at least a 98% satisfaction rating. I shopped for about 3 months. I was down to a Pfaff Creative Sensation Pro and the Janome Horizon MC14000. I chose the MC14000 because of the seller's reviews and the price. The machine far exceeded my expectations. If you want to talk about specific sellers and techniques for weeding out the bad ones, you can PM me.

I bought a Bernina Artista 730e. I contacted the seller and questioned him very thoroughly about the machine and had him agree to 30 days trial. The machine was $4000.00. It had been the display machine in a shop, so it was nearly new. This was in 2004. I love the machine. I got all of the hoops, plus the materials they used for training new machine owners. I am still using this machine. I feel I got a very good deal.
i feel with eBay's policies and PayPals policies, the rating systems (his was 100%) that it was safe. The machine came packaged in its original packing and was fine.

I've purchased three vintage machines on E-Bay, plus a Brother PQ1500s, with excellent results on all of them. I checked the sellers' ratings, communicated what I expected via packing, and all four machines arrived in great condition. The Brother was shipped in its original box, and the others in a combination of bubble wrap and styrofoam.

I have bought and sold machines on eBay, no problems.

I have purchased 3 very expensive machines and have been pleased with them all. I contacted each seller prior to purchase- I always ask why they are selling and enter into a conversation with them.

I bought a featherweight.... no problems