To the original poster ...if you like the chocolate yorkie, go for it! now 6-7 weeks old for new homes , it's too young , I would be concern right there.
the price of $600 I think is great....make sure the puppy looks happy and healthy and if they can give you some sort of health warranty to at least until it gets checked by a vet.
I myself stick to the AKC standard but respect other breeders no matter what their beliefs are or breeding program they have .
Good Luck