Whatever military branch your son chooses, encourage him to enter the aviation community of that branch...Army Air, Marine Air, Naval Aviation, Air Force, or CG Aviation...much better living and working conditions, IMHO.
For example, when I was a single guy working the avionics systems of the F-14 in a fighter squadron aboard USS John F. Kennedy, I was able to live in a barracks (or rent a house) on land after a six-month deployment, while the "black shoes" had to remain and live aboard ship.
I'll have him check that out, good advice, thanks... And he probably would really enjoy it.