GSD is a sickly breed and it is a trouble to get a puppy matching description of the breed in Wikipedia. Health is a problem number one, mental health is a problem number two. I wouldn't trust any breeder, whose dogs weren't evaluated at the dog show (it requires independent medical checks) and have no marks at Schutzhund competition. Both are terribly important. GSD was called a "plasticine dog": every GSD has a potential for being agressive, to be a companion of a social worker, to be a sports dog in Schutz competition or Agility, there is nothing what GSD cannot do provided you train your dog in certain direction from the very first day you get him. But, here lurks the main trouble having GSD - his training must be continuous, it takes time, and you simply cannot leave your dog without training. Vertually, plasticine dog - is time consuming dog. If you are not sure you and your spouse can devote 3-4 hours a day to your dog for the next three years - it will be better to think about some other breed which doesn't require prolonged intensive training. The difference between GSD and Golden is that between a rocket and the balloon.