My boxer(male) 7 mths old....

Question
My boxer(male) 7 mths old. He doesn't bark when someone rings the doorbell. He doesnt bark at strangers. The only time he barks is at me, when I'm playing with him. I got him as a watch or guard dog and also as a family pet. I need your help.  

Answer
Good dog !
I will trade you one of mine that barks even when a leaf blows across the lawn, for your's that doesn't bark. They drive me nuts.
They know mom is old ans doesn't have the energy to mess with them.LOL
Barking doesn't signify a good guard dog.
One that does not bark at strangers will keep you from having idiots constantly calling in complaints that your dog is trying to attack them.
At 7 months old he is still a baby.
Train him in obedience .
Classes at Petsmart and Petco on the weekends are great. They have qualified trainers that teach you how to train your dog, give the proper commands etc, and are there to observe you so you will be sure to learn the proper way to handle them.
Once you go through the basic obedience course, you will know how to train any dogs you get in the future as well.
Treat him like a member of the family, praise him for being a good dog for not barking. That is a well behaved dog you have there.
You don't want him barking at everybody.
When someone who shouldn't be there tries to come in the door, or he thinks a member of his family is threatened, he will do a lot more than bark.
Charlotte