As the wife of a 16 year regional captain, I'd say, don't do this to your future daughter-in-law and grandchildren!
Airline hiring is very cyclical. It has been very depressed for the last several years. With the first round of the new age 65 retirees coming, expect some movement in 2012. This is however subject to economic pressures and the cost of oil. The cost is already getting to a point that airlines will start struggling again. Most of these costs are not passed on to the passengers in the way of higher fares , although some do charge fuel surcharges, but are actually carried on the backs of employees in the form of wage cutbacks, hour cutbacks, increased workloads etc.
It is not common for pilots to have 18-20 days off. At the airline my husband works the newest hires that sit on reserve are currently only getting 10 days off per month. After 16 years my husband sometimes gets 18 days off monthly. Pilots are generally only paid from the time the door closes until the time the door opens again. They spend twice as much time as that on duty though. Pilots at the regional level, which is where he would start out if he went the civilian route for his education and training, start at around 22,000 dollars a year. Some perhaps pay slightly more or less. Layovers are really short, barely enough time to sleep, the pilots are definitely flying very fatigued every day! So much for the glamorous life of a pilot!
Go the military route if possible, then if he is unable to get a job when he gets out, as hiring is very competitive because there are thousands of highly qualified pilots currently on furlough, he can stay in the military while waiting for the tide to turn. Then he also won't have the debt of his education and training hanging over his head. Very few airlines (FedEx is one) offer a pension plan any longer, most were gutted in bankruptcy courts over the last few years. Most now offer defined contribution plans and the amount of company match can vary widely amongst the airlines.
Pilots can travel free on most other airlines on their jumpseat. This depends on the airline that you work for and the reciprocal agreements that they have with other airlines. Spouses/domestic partners, parents and children get pass benefits, which can be free or at a very reduced rate, but they are on a space available basis only. This means that you only go if a seat is available, not so easy to do anymore. When my family flies, we buy tickets like everyone else!
He could possibly get hired at a few regionals without a college degree, but I can't think of a major that would hire him without one. The cost of his ratings will run very high and then he will have to gain enough hours to be competitive for interviews/hiring. This usually comes through flight instructing, but there are a few other avenues to gain those hours. The feds are in the process of raising minimum hour requirements for hiring too so it will take even longer to get those hours. Also soon, first officers will have to have their ATP license as well to get hired.
The lifestyle is very hard on families, especially at the regionals because the hours are long the pay is low and families are apart for long stretches at a time. Usually these are families that are young and just starting out so this is more stressful. Divorce rates are high in this career choice. It takes a strong and independent wife/husband to be able to stand this lifestyle. It takes a toll on kids as their other parent is often missing birthdays, holidays and important school events.
It starts out exciting but after a while it turns into just a job for most pilots. Don't get me wrong, they all love what they do, and even when complaining, most wouldn't change what they do. There are some advantages in this career, but you have to be able to stick out the really tough parts to get to them and be able to enjoy them.
Remember, this is my perspective, the wife of a regional guy, but if it tells you anything, my husband is 45 and is already talking about how hard it will be for him to make it until 60 let alone 65. Plenty of guys medical out for health reasons all the time. We are saving like crazy and trying to get our house paid for so he can "retire" the airlines at 60.
Have him do a search for airline pilot forums on the internet. It can be an interesting look at life from a pilots perspective. It can also give him an idea of the qualifications he will need and what it takes to get hired and what hope he has of making it to the majors. He is young and if the timing, which is just about everything, is right he will make it.
Pretty long winded, but it gives you some idea of what it is like. Sounds positively delightful, doesn't it? It certainly is not the career it was 20 years ago. As for me, well that was cheaper than therapy! Good luck to him in whatever he chooses!