I've only had dogs since I moved out on my own, none as a kid, we adopted three shelter specials over the years after getting a house, all adult pit bull mixes. We also fostered several dogs of various breeds for rescues and friends. Currently have one senior bulldog/pit mix left and a Presa puppy. I wouldn't really recommend a guardian breed or one known for aggression like a Shar pei for someone without a lot of dog experience. Most dogs are much more bark than bite and that's generally enough to deter home invaders, a dog that would be an actual threat is going to require a great deal of training, time and extra care, many insurance companies won't cover dogs known to be aggression also so that's something to consider also.