I know of a father daughter cross and was wondering What the breeders opinion was. This is a working GSD line. So far pups seem good just wondering if this cross is a bad thing.

Depends.... I have seen inbreeding/linebreeding that close that have had decent results. I've also seen it go horridly wrong even when both father and daughter or mother and son in this case were decent animals on their own. Take a wild guess what I've seen more of? The problem most breeders have when they attempt line breeding is that they are trying to replicate an animal which has already been born. This is IMPOSSIBLE.

My first question to this breeder would be why they would choose such a close crossing and what their expected end results would be as part of their goals. The other would be what was so special about this dog pairing that they are trying to encourage traits from. Even super experienced breeders don't necessarily have the saavy to understand how line breeding programs work, or the sight in mind to really pull it off. What bit I know came from line breeding experience was with animals that don't have the mental, long term health, and other complex components that are required for a good dog. Line breeding dogs is the same principle as line breeding a cow, pig, or goat. The problem is that you can't eat your mistakes but rather may have a litter of puppies born that may have to live with them.

Finally this kind of line breeding is bait for animal rights activists. There is a reason you can no longer register mother son/father daughter crosses in the UK Kennel club registry anymore. So keep that in mind if there are any genetic health issues that occur in this line. People will immediately blame it on the linebreeding/inbreeding which may be valid or may be not.

Technically Chris, a father-daughter breeding is inbreeding (not line breeding). Melissa's answer was excellent.

Personally I would not buy this puppy, especially if I were planning to breed it someday.