Romasik,
Many variations on a theme to your questions. I can bloviate from the front porch of Ye Olde Pilot Retirement Home and say what I wish I'd done.
The longer a person like your son, or any of us for that matter, flies for a living the more plausible the avenue of turning flying experience into non-flying aviation dollars becomes should that be necessary. It requires some prep work along the way by getting involved in things like sim/ground instructor, check airman, safety committee work where additional skills and experience can be gained (and contacts made). This may require working for a company (and/or a company having a union where such options exist) large enough to have these functions in-house. One example might be a person with a psych degree getting into the human factors arena in a safety organization. These committees are always in need of volunteers.
Aircraft dispatching also comes to mind. If a license is required in a particular country, the body of knowledge will be essentially identical to ATPL subjects and can be obtained along the way with minimal effort and expense. Just one idea...others may come to mind.
I've known people who did all of the above; they were the smart people.
Having your son aware of this stuff at the start is valuable and he's got the advantage of having you to advise him.