He is being advertised as a "malti-poo" which is a cross between a maltese and a poodle. It appears that could indeed be what he is. I would caution you slightly about purchasing a pet over Craigslist... you just need to be aware of what you are getting in terms of health. Ask questions about the veterinary care he's already received (vaccines, deworming, etc). Its also odd that they say that he's a male, but then go on to refer to the puppy as "she."
Good luck, and thank you for asking Petco Pet Education Center, formerly Petcoach!