What should I pay attention to when buying?
The same as in any second hand marketplace, really. Personally, I look for:
* Details of the person I'm dealing with; have they been active for a long time on the forum, and have I interacted with them? Are they well-regarded, overall?
* Is the seller a commercial trader or is it a private sale? Either is fine by me, but my expectations of the transaction tend to be a little different; a commercial trader will generally be more forthcoming in proactively offering transaction mechanisms, that are often more or "less take it or leave it", whereas the details worked out with a private seller tend to be more collaborative and jointly determined.
* On Photrio, sellers (and buyers) may have transaction feedback you could use as a reference. If you go the the Classifieds and click the username on a person posting there, you often get a button that says "Transaction feedback". You can click this and view a very brief summary/evaluation by people who have traded with this person.
* What's my financial exposure? I.e. how much can I afford to lose if it goes belly-up? I might be willing to take a risk on a $50 item, but a $1000 item is a different story.
* Where's the item located? This may be less relevant to you, but when we in Europe import stuff from abroad, we have shipping costs, import taxes and inspection costs to contend with. I always make a rough estimate of this overhead so I know what the real amount is I'm looking at.
* What are the shipping and payment options, and are they to my liking? Most sellers offer something like PayPal or (in Europe) a direct bank transfer, which is generally safe and reliable for both parties. Sellers who demand cash in an envelope...nah (extremely rare nowadays; used to be quite common in the past). As to shipping, is the seller offering a shipping option that seems viable/sensible for the item in question? If you purchase a 20lb large format camera kit and the seller offers a $15 flat rate shipping option across half the globe, something isn't right.
* How is the overall communication with the other party? Are they reasonably quick to respond, and do they answer questions and pick up on important details? Or are they slow to respond, with very brief messages that only press for payment?
All of this is basically a long way of saying "use common sense". My experiences with online purchases through photo communities (including Photrio) have always been positive. In that sense, I estimate that the risk is low, especially on Photrio, which is a fairly close-knit community anyway. Stories of scams conducted through this site are very scarce; in fact, I'm not aware of any recent examples.
