I had a boxer that was a great dog. She would even check the heartbeat of a gentleman that was staying with me while he recouperated from a heart attack. He was such a story teller I didn't believe him until I saw her do it. However, you really should try to get a dog that's been specially trained. Trained dogs, even though they're large have been trained to stay with their person and won't do a lot of roaming or getting in the way. Also, by the time they're trained and placed they're out of the puppy stage. Check with some of your local fraternal organizations, like the Lions, Elks, Moose, Eagles, or Masons and see if they would help defray the cost.