Having just had a ghastly experience with a unsocialised Labrador puppy that we bought before Christmas I would certainly check the breeder will take the puppy back if you find it unsuitable and this is backed up by a vet's certificate and GET IT IN WRITING. My experience was in France where we live but was truly awful, we gave the puppy back to the breeder as she proved to be so aggressive and dangerous and I feared for my children and all our neighbours' children. The cheeky sod promised a full refund in due course by bank transfer and then completely changed his tune the minute he had the dog back. He even tried to claim legal rights over the dog by fabricating a story that we had abandoned it on his doorstep (sure, who makes a 5 hour round trip to abandon a dog??) My children lost their savings and we spent weeks living with the guilt of not having been able to do anything about keeping the puppy. An unsocialised dog is not something you can easily spot in the breeder's home.