Companies on the Internet - how to check if they are reputable?

What prompted me to post this thread is a company on the Internet offers used Corvettes for (what I think) are ridiculously-low prices. (For example a 1974 Corvette for $6,000 - the picture looks great but that means nothing.)

So, is there some sort of Internet “Better Business Bureau” or a clearinghouse where information such as this could be obtained?



Thanks for the reply. It seems to be a great site.