What is your background - what camera have you used till now? Do you want this for a one-time occasion, or will it be the start of a longer term hobby?
I bought my first DSLR (Nikon D40) on craigslist in 2008. And I've bought all sorts of related stuff (lens, filters, tripod, replacement camera D90, etc) on CL, and have never had a problem. I always recommend CL to everybody.
Before I bought the D40 I had never used a DSLR, other than trying a Sony a100 or something in BestBuy (which was what made me want DSLRs). So it is possible to come out ahead despite everything.
My advice is
a. Buy from individual photographers, not shops (or - horror - pawn shops ).
b. While professionals get rid of older stuff very regularly, the amateur selling off is a better source for you. Particularly the ones who buy in haste, and then realize they can't handle a big camera. How do you find out? Simply ask why they are selling it, and apply your truth-o-meter.
c. While the box, the manual, etc are not really value, their absence only tells you that either the stuff is really old, or the guy is careless (might as well mean he also banged up his camera), or stolen stuff. Not always, but possible. (My D40 did not come with box or manual). Try for the ones that have all that included.
d. Be patient. If you don't see what you want at the price you want today, tomorrow is another day.
e. Don't buy a DSLR as your first ever camera, or at least before you have used some p&s camera a bit. You should know the basics of photography - can you recognize an out-of-focus picture (so many don't even know)? flash usage, depth of focus, etc. Why - because without all that you don't know how good a DSLR can be : how will you know if the camera is functioning fully? (But then, this applies to before buying any brand new DSLR too, so not really CL related)
f. go Nikon. Not wanting to start something here, and I might be biased, but I feel Nikon offer more functionality even at the lowest end of its models. That said, even the lesser known DSLR brands of Sony or Panasonic have their proponents.