I think it also really depends on the seller. I have seen chins on cl that are in horrible condition, but I have also seen ones that are very well taken care of.
I actually just got a 6mo old male mosaic via craigslist. The guy was very nice and knowledgeable. He had rescued two chinchillas at different times and kept them in separate cages. He was told they were both males but one ended up being a female. So he went and got the male neutered and waited the appropriate amount of time before putting them together in the same cage.
Well apparently his male bent the rules, lol, because thats how my lil guy came to be, whoops. So technically he was an accident, because the guy had no intention of breeding them and tried taking the necessary steps. And he said he wanted to find the little guy a home otherwise he would neuter him as well, but he said he would rather not get him neutered if he didnt have to.
His rescue chins had the right cage, all the right supplies, and were eating the right food. And he was asking a very decent price ($100), I didnt even haggle with him because I felt the price was very reasonable.
So it goes to show you that not all craigslisters are scum (but many are, lol)