i have bought equipment off of craigslist. just dont meet at your house and dont buy anything which is illegal where you live. the seller usually just wants to get rid of their stuff and they need the money if it seems like they are interested in anything else i would be suspicious. they should not need any personal identifiable information from you pay cash.
I agree with the above, don't buy on the promise of "I'll ship it to you"
Pay cash, and if you are going to the sellers house, get your buddy to drive you.
Buy bulbs new.
Clean everything very well before you introduce it into your growing environment.
I occasionally see grow equipment on CL or similiar sites, and there are some good deals to be had. I recently responded to an ad, which turned out to be from a grow store and got myself a GH aeroflo36 for MUCH less than retail.... it ships today! (oh, that last line contradicts my earlier don't fall for "I'll ship it", but I checked out the store and had my local shop vouch for the guy!)