Ebay is a wonderful online flea market, but unlike a real flea market, you cannot pick up the item and inspect it or easily strike up a conversation with the seller. So how can you give yourself the best chance of coming home with a good camera and not ending up with someone else's junk. Once I find a camera on eBay that I am interested in, here are some steps that have worked for me:
What camera to get. This is a personal choice but a few things to keep in mind may help in making up your mind. A late serial numbered Arriflex 16S/B will give you the most options when it comes to lenses as it contains one bayonet mount in its three mount turret. If the camera has a serial number higher than 15,000, ARRI will still service the camera and can get most replacement parts for it. A close second would be the majority of the other Arriflex 16S cameras made, with the only exception being the earliest models with the Flat Door and Zeiss viewfinder (see the "History of Arriflex 16S in pictures"). These can be harder to service and replacement parts are pretty scarce.
After you find a camera, find out as much as you can about the seller by reading his feedback. (I realize that men and women sell cameras on eBay, but for brevity sake, I am just using the male pronoun instead of trying to use both). It is nice when the feedback is 100% positive, but that is not always the case. If there are negatives, scroll through the seller's entire feedback history and make note of every negative. If he has feedback like "Item not as described", "no refund", "dishonest seller", those obviously should send up red flags and will require a convincing explanation from the seller before you place a bid.
Take a look at the auctions the seller has been involved in. Scan through the feedback and note how many feedbacks were from buyers and how many were from sellers. This can tell you alot. If his feedback is usually from buyers, that may mean this is a small business for him, which may make him more interested in happy customers. If his feedback is usually from sellers, it can indicate that this may be a one time thing and he has a camera he wants to sell. Knowing this information can help you judge how to approach the seller when you "Ask seller a question", which I do on any auction I bid on.
Look at as many of the seller's previous auctions as possible to see the history of what he buys and sells. You do this by clicking on any blue auction numbers in his feedback list, these are hyper linked to the original auctions and can tell you what the seller has been buying and selling of late. In the last two months alone I have found one seller who had just bought a basket case Arriflex 16S and some pretty shoddy lenses and had cosmetically cleaned them up and was selling them with a 'Buy-it-Now" price of $2750. And when I went through his feedback, I saw how he was repeatedly doing this. I also found a second seller who had just purchased an entire 16S package of early vintage and was selling it, claiming it had been his camera all through film school, that he had shot all of his short films with it, and how it had given him spectacular images; when in actuality he had only had the camera for a few weeks.
Use the "Ask seller a question" link. Once you have done your research on the seller, ask him some questions about the camera. The most important question I always ask is for the serial number off the front door of the camera, right below the viewfinder tube, and the serial number off the back of the camera. These have to match. Let me say that again. THESE HAVE TO MATCH. ARRI used a number of different viewfinder assemblies over the many years of 16S production, and the viewfinder in the camera door, and the viewfinder prism in the camera body, were matched sets. You do not want to buy a camera that has a body and prism off of one camera and a viewfinder and door off of another. (This is my own personal thing but I find it best to ask this question in a way where I ask for the numbers separately, like I wrote above, as opposed to asking, "Do the serial numbers match?" Asking the latter can many times elicit the response, "Oh yeah, they match." Whereas, asking the former has gotten a number of sellers to honestly tell me the numbers were different.) After I've asked about the serial numbers, I ask the usual questions, "Why are you selling the camera?", "How long have you had it and when was it last serviced?", "Have you shot any film through it recently and if so, is the footage posted anywhere that I can see it?" And finally I mention to the seller that I may be in their area (their location is listed in the auction) and would it be okay if I came by and looked at the camera. Anyone who offers to let you come by and inspect the camera I feel is being honest about what they are selling. Compare the answers you receive with the other information you have learned about the seller. If everything checks out you can feel a certain degree of comfort in bidding with this seller.
And finally, the most important thing, give yourself time. Figure on a few months at least. Watch the auctions, bookmark the cameras that you think may be a good value and then track them through the whole auction. Watch what happens in the last thirty seconds of the auction, and the reason I say bookmark the auction is that as soon as it is over, it will disappear off eBay, but if you bookmark it, you can still view it and see who bid what. This will also give you the opportunity to see the many shady dealers on eBay. They keep coming back again and again. Be cautious of people who have (0) feedback and after you have watched the auctions for a few months, you can spot the scammers who copy pictures from other auctions and list them as their own. Be aware of the hype, the sellers listing the camera as "best on eBay" or "camera you've been waiting for", etc. And watch what cameras get listed again and again. Unfortunately folks think they will grab the "diamond in the rough" on eBay, but in reality, that rarely happens. Most of the cameras are old and in need of at least minor service. But that is okay, if you budget for that. Because once you have your camera, and it has been serviced, it will give you years of happy shooting and great images.