Private Treaty Breeding can meen sevaral differt things.
Ofren it refers to a breeding between a champion stud and a leased female
or stud fees have not been paid and pups sold are retained by stud dog owner
either way best advice on buying a pup or started/finished dog is getting paperwork when monies are exchanged
http://www.doubleaquailplantation,com/gsp_english_setter_stud_dog.htm