No, he absolutely does not have to have a purebred. He came to me for suggestions because his main concerns were that they didn't want a repeat of the major damage that was done to the yard by the previous owners dog and his concern about it being left alone for 10 hours. And again he is not worried about digging, he is worried about major damage. I think the only specific thing he really wants is that it is a medium to large size adult dog. He was just looking for other suggestions as to what to look for. We have already spoken about not leaving the dog out alone without supervision as the best way of avoiding unwanted craters, uncontrolled barking and fence jumping, as well as being important to the safety of your dog. I think he is going to be a great dog owner. And he went home with four petfinder printouts to show his wife tonight.