Assuming he lives in the united states is not enough. It is not legal in all 50 states to carry a concealed weapon
It's a reasonable assumption though. There is only one state (Illinois) in the US which completely outlaws concealed carry. The other 49 states all have some variation of concealed carry law in place. I'll grant that in places like California, New York or Hawaii it's difficult to obtain one unless you're wealthy or have the right friends, but many of us live in more enlightened states with "shall-issue" laws in effect.
As for businesses and schools, you simply have to be aware of the laws of your state and behave accordingly. I don't carry on school property and I've stopped doing business with companies which choose to disallow carrying on their premises. It's really not that complicated.