[PyrNet-L] help

I have never owned a GP. Someone has offered to give me a 2 year old male. They have 3 and would like to find this one a good home. I don't know enough about this breed to know if I should take him. I have a 4 year old son. He has met the dog and they played beautifully together. Should I worry about him becoming aggresive? Should I start with a puppy. Do they train easily to a underground fence? Also, his rear feet look funny. They don't have that cat like appearance.He seems to walk on more that just his pads.Does anyone know what I mean? I need help. Should I or not? He also moves a little funny in the rear. Help!!!!