Active duty Air Force and Air guard are very different as far as the life, schedule, benefits, etc. Is he thinking about doing the Air Force reserves or going active?
For the Marines:
During boot camp - at family day and graduation
During MOS training - a weekend or two depending on how far away you live from it, unless it's long enough that they'll let you move with him
After training (in the fleet) - it varies widely, for myself, in the past year my...