There are several questions commonly asked about buying or selling a bike or bike parts over the net from a private party you've never met.
I've bought and sold a few bikes and tons of parts via usenet since the late 1980s. It's usually not a problem -- I've never been burned on a deal, either a buyer not paying or a seller not shipping the goods as promised. Sometimes parts haven't been exactly what I expected or payment has been slow, but that's no big deal if everything works out in the end. I've also done a lot of buying and selling on web pages such as eBay, and while there have been a few bad deals, most people still seem to be honest and reasonably reliable.
As a first check, does the person have a meaningful userid at a reasonable system? e.g. their login is something based on their real name, their system allows 'finger' requests, they aren't posting from AOL or other easily spoofed, pseudonym-riddled sites, etc. (AOL is a particularly easy system for dishonest people to abuse -- the company floods the U.S. with free new-account disks, and allows customers to post under false names with no permanent link to the customer's real ID. I'm not saying they're a bad company, but I would never trust someone whose only identification is a pseudonymous AOL address.) Once you've established that the email address really exists, then it's time to get a real name, address, phone number, etc.
For valuable items you might want to verify the person's address and identity, perhaps checking with a directory service to get their phone listing and address and seeing if that matches what you get from them in email. Infospace is a good service for this sort of lookup.
Look on a service like DejaNews or AltaVista to see what else the person has posted -- I'd be a bit wary of anyone whose very first post was a cool bike for sale at a great price. Also if the person has trouble describing something he's selling. You don't want to buy a repainted Huffy or a box of bricks.
For small stuff, get a detailed description from the seller: model numbers, amount of use, condition, sizes, etc. Make sure you agree on what terms mean -- "new" may mean still in the manufacturer's box to me, but you might consider a stem "new" if it has been installed and removed with no serious use, while I'd call that a "takeoff" part.
For a whole bike it gets more complicated. First you'll want to define exactly what the bike comes with to see if it's what you want -- what size is the frame, and how is it measured? What components does it have, what condition are they in, etc.? In the case of parts that come in different standards, which does it have -- what size of headset, seatpost, rear spacing, bottom brakcet threads, etc?
Ask the seller about refunding your money if the bike isn't what was advertised. Photos of the bike are a good idea, either mailed to you or posted on the seller's web page -- they describe the bike in more detail than words alone.
If you're buying an expensive bike from someone you don't know, it might be worthwhile to have the person take it to a bike shop and get the mechanic to check it over for condition and quality and send you a short note on it, preferably on a sales slip printed with the shop name and phone number (to make sure the mechanic isn't really the seller's roommate on another phone line.) Some bike shops will also pack and ship the bike for a reasonable price, or even ship it to another bike shop that will put it together for you and tune it up when it gets there.
For cranksets or anything smaller I usually ship via priority mail since it's simple and cheap. A triple crankset fits in a Priority Mail 2 lb envelope with enough padding to withstand shipment and costs $3.95 for 2-3 day delivery.
On something as big as a bike I prefer insured UPS/COD shipment. A good bike box will have a couple of hand holds that are usually emphatically labelled as "inspection" holes so you won't complain to the box maker if they rip out from handling. The Cyclists Yellow Pages has a good article on how to box a bike for airline travel -- UPS is similar.
Even if your UPS driver won't let you open the box before paying for it, you can at least see if there really is a bike in there. Have the insurance be enough to cover any losses, and inspect the bike for damage ASAP.
PayPal has taken much of the uncertainty out of on-line transactions. You can accept or send payment by credit card or EFT to individuals in many countries, and know in advance that PayPal has verified their address and account information. It's a big step from sending cash in the mail when people weren't sure they could trust your out-of-twon check.
On small things I usually rely on the honor system if the other person seems reliable. For example, I just agreed to sell an extra pair of pedal cages. I'll put them in the mail to the buyer's address tomorrow and email him the total cost, and I trust he'll mail me a check as soon as convenient, but I won't deposit the check until he says he got the cages and they are in fact what he wanted. If he doesn't want them I'll send back his check when I get the cages back.
Some of this may sound like a hassle, but it's really not too bad, and most of the time you won't need any of these precautions on small stuff. Especially if you recognize the name of the person you're dealing with as being a long-time poster -- few ordinary people want to ruin their good names by screwing people over in a public forum.
Finally, if things don't seem to be going well, email the person and give them a reasonable time to explain. Sometimes mail gets lost or delayed by storms and floods, sometimes people get busy at work, etc. Don't sound a false alarm when a reasonable person could just be running a bit late.
This page written by Josh Putnam. Please feel free to email questions, comments, corrections, suggestions, etc.
© Joshua Putnam