Now, my experience will the e-biz here tells me that most locals have yet to comprehend how it works... But in order to comprehend that, they would have to understand the true meanings of things like competition, marketing, selling (not just tying to play tiguere) is. And that, while still considering myself to be young, I doubt I will get to see.
You will still see ads, even in newspapers, for cars... and no price. Sure, aren't we all dying to run to that dealer and listen to his BS just to find out that he has only fantasies?
So, e-sites are a good way to see what's available, what's is popular and to get an idea about the maximum price.
Buying or even selling a used vehicle from a local non-dealer is worse of a night mare than dealing with a big mouth dealer. At lest they are ready to do a deal, have the papers, can handle the deal money wise and do understand the legal steps to be taken (after trying to fool you into believing that "this or that" is not necessary).
Good luck and if in the slightest doubt, don't hesitate asking here BEFORE you do a deal or sign anything.