Aggression Problem

Question
I saw an ad in the locals section for someone selling a black German shepherd.After talking to the owner for some time, this is what I know about the dog:
2 years old.
Friendly towards animals, stranger dogs included.
Friendly towards owner.
THE ISSUE- the owner says she nips at the heels of strangers coming into there home. She has never bit, like attacked someone, but she growls and makes quite a fuss.The owner is selling her b/c they travel a lot and don't want to be liable for her biting a pet sitter. She said she has had the dog since it was a puppy, and this was never a problem until she had a litter of puppies. After the puppies were taken away from her, she started this aggression.

My question to you is, is this a fixable thing? I do not want to buy a dog (she is papered) who will be biting my friends. Although I live by myself, and being a single female, a guard dog does have its perks. Thank you

Answer
It would be speculative to say how easy it would be to correct the problem.  You might do better to find another dog without such a problem.  There are plenty around, we slaughter millions a year for lack of homes.  One of the best sources for dogs with a predictable personality is the rescue dogs. These are dogs that lost their home, but were taken into a foster home to be retrained as necessary and placed in the right home for them. You may find a rescue near you starting at http://www.akc.org/breeds/rescue.cfm The rescues charge a fee to help cover their expenses, but is much less than the price of a puppy plus all its medical expenses the first year.