Well, I would definitely want some more info on the age. No way this baby is 6 weeks old.
I usually tell everyone to be very very cautious of Craigslist. With that said, I found Mandie on Craigslist. I was very blessed. I like that she has the paperwork and the pup is microchipped. I would call and talk to her about it. See where SHE got the pup..who the breeder was..ask about vet visits and records...go from there.
The puppy is adorable!
ETA: If I were you, I'd call fast before someone who doesn't have the pup's best interest in mind tries to scoop her up....