Knowing that your dog is on the lookout for intruders can bring a lot of peace of mind. Just having a dog that barks at any suspicious activity can ward off potential threats.
There is a huge difference between a guard dog and a dog that is trained for protection work. A guard dog is trained to carefully keep an eye on your property and alert you when something is out of place. A protection dog is trained to protect his owner and to bite and hold down an attacker. Protection training should only be done by experienced and professional individuals. A protection dog must be extremely well trained and under control at all times.
While you are teaching your puppy to guard your property, continue to socialize him around people outside of your home. When he meets a new person tell him to 'Say Hi' and have that person feed him treats. Do this so that he will learn the difference between normal human behavior and suspicious behavior so that you can let him know when someone on your property is supposed to be there.