OK, I'll start by saying that I'm totally unqualified to give advice on buying a sewing machine. I've only ever used two -- three if you count my mom's machine, which, as a teenager, I once used to make a bathrobe (I still wear it!) but otherwise never paid much attention to. I don't even know enough about the machines I do have to take full advantage of their features. That's why I'm recommending these two articles, by really smart and crafty bloggers, Erin at A Dress A Day (link) and Megan at Not Martha (link).
That said, I do know about the perspective of a beginner searching for a used machine, and wanting to find something reliable on the cheap. One of my main concerns was that I'd lay out a lot of money for a great machine and then find myself losing interest in sewing. I mean, I really enjoy sewing, but the time I have available for it varies according to my work schedule and my son's nap schedule. And, honestly, I'm depressingly bad at sewing. I learn something new with every project, but I still keep making major mistakes that require what seem like weeks of futzing to render each item wearable. And many of them are wearable only at home, or under sweaters! While this isn't yet putting me off the whole enterprise, I know myself well enough at this advanced age to be aware that I might lose steam if my learning curve doesn't pick up soon. Thus, my big requirement: affordability.
I have often seen the suggestion to buy a used machine from a local dealer or repair shop. However, there aren't many choices in my city. There's one shop, which had only a few used machines, none of which rang my bell. (This might be because I'd been looking at some of the beautiful older machines available on eBay, and these were all bland-looking 90s-era machines.) Still, my point is that this might not be a viable option for everyone, so don't feel bad if it doesn't work out for you. If that's the case, I'd definitely check out Craigslist and Freecycle before I'd buy a pricey new machine (or a cheap new machine, as my experience taught me) I've seen really cheap sewing machines on the former, though they rarely post pictures and often don't even include details, so you'd have to call. Freecycle machines would be free (obviously), but the price you'd pay would be all the time spent reading the offerings constantly so you don't miss the few that get posted
Even better, borrow a machine from a friend or family member to start you out (I'd hand my Singer over in a heartbeat to a friend who wanted to start sewing, both to have it put back in use and also to convert said friend over to my sewing obsession). Or shop at garage sales. Or thrift stores. You don't want to get started on a machine that's only going to frustrate you, but if the price is right and you can see that it runs and the needle goes up and down, you have a good chance of getting a steal.
Oh, and a major caveat for old machines: If you're a beginner, you want a manual or you'll never even get the thing threaded. If the machine you want to buy doesn't come with one, search online -- lots are available on the internet.
Another good thing about older machines -- I'm talking about mechanical ones, without computers -- is that you can do basic maintenance yourself. The manuals tell you how to open them and where to put the sewing machine oil on a regular basis. I had to replace the main belt on my White right after getting it -- luckily, our one sewing machine shop had the belt I needed in stock (they'd be able to order it otherwise), so I bought it and installed it according to the manual's instructions. I could see that it was slipping when I ran the machine with the cover off -- it was beautifully simple to diagnose and repair.
So, my experience: I bought the White off eBay -- it was, in fact, my first ever eBay purchase. It worked out great, and I have no complaints, but I can easily see how one might get screwed. Here are the things I think you should keep in mind:
1. Shipping costs are really high. Old machines are heavy, and they require really careful packing, so this isn't surprising. That said, some sellers appear, to me, to be overcharging for shipping, possibly for extra profit. I emailed one seller in my state about a machine, asking if I could come in person to pick up. They wrote back that I could not. I think they were charging some $50 or so for shipping, so this, to me, was a tip-off that they were building that into their profit. The shipping for the machine I did buy was about $30 -- definitely on the low end.
2. A lot of sellers claim to be professional repairers. Maybe they are, but I wouldn't assume they're telling the truth. Still, it's a no-brainer to check their past sales -- if they sell a lot of sewing machines (preferably only sewing machines) and have great ratings, then they probably make a point to sell nice machines in good shape. The seller I bought from offered to take the machine back and refund my money when I talked to him about the slipping belt -- these guys really want to keep their ratings up.
3. The other type of seller I'd consider buying from is an individual who is selling his or her own sewing machine. Sometimes they claim to have had it serviced recently -- ask them to show a photo of the receipt as confirmation. Make sure they know how to package it -- the guy I bought from packed my machine into a box wrapped in bubble wrap, and then put that inside a bigger box filled with packing peanuts. This seemed to work -- I can't claim any expertise in packing machines, but be sure the seller is aware that they really have to cushion it and be super-careful.
4. You've probably played around on eBay before, so you probably know this: Don't bid until the auction's almost over. If you bid early on, other people will swoop in at the last minute to outbid you (if it's a good deal). Watch a couple of auctions to see how this works.
5. Some machines seem to be really trendy on eBay -- Berninas, in particular, go for hundreds of dollars. Maybe they're worth it -- I honestly don't know, but it seemed to me like paying $700 for an 830 Record would not be as thrifty as I wanted to be. My impression is that, on eBay at least, you should watch out for trends that drive up the price of certain machines beyond their real value.
I hope we'll get some reviews of these machines -- and others from eBay and other sources -- on this site soon, so we'll have a better idea of how much they're worth! Please add comments about your experiences buying used, and any tips you gleaned from the experience so that newbies will have a head start in extending the useful lives of great old sewing machines!