What type of German Shepherd are you looking for? What do you want the dog for?
When choosing a breeder you need to be very careful. You don’t want to buy a gsd that have these horrible angels in their back and hind legs which is causing suffering. The health and mentality status needs to be investigated and documented for the breeding parents, relatives and ancestors. It doesn’t say much if only the parents are tested.
The diseases and defects they should be tested for, or proven not to be a recurrent issue in the lines, are at least; HD/ED, hemophilia, skin diseases and allergies, eye issues (RD etc) and degenerative myelopathy.
The mentality needs to be well documented through out the lines. Preferably through a mentality program and tests, but I’m not sure how that works in the U.S.