We bought our border terrier from a breeder in Kent 2 years ago, she was 5 yrs old and was his breeding bitch who had fulfilled her purpose and was no longer needed….the area was beautiful, driving past old houses, quaint villages and we rolled up at the scruffiest house in the area, smelly, full of dogs etc, but we took her home ( after an 8 hr drive back to north Wales ) bathed her, wormed her and took her to the vets for a check up. She has been fine.
My advice is to get the dog, all the necessary paperwork, reciept, and when you get the pup home, visit the vets for a check up( for the dog, obviously).