Let me add to my earlier reply. If your son wants a major airline career, a DD will be very tough to overcome. The airlines will even go so far as to request information such as credit checks. In such an environment, only the candidate who looks best on paper will even get an interview. HOWEVER, if your son is willing to settle for a mid level pilot job, and he now exhibits a newfound sense of responsibility, and he has remained squeeky clean since the DD, he should have a decent chance at gaining meaningful employement. There are numerous jobs available that offer decent money and working conditions, but most pilots consider them stepping stones to an airline career; some of those companies actually look for people such as your son (assuming he has changed his ways) because such people are more stable in the mid level. Simply put, employers get tired of the continual turnover, and welcome people who can't leave for greener pastures.
If he decides to continue he needs to be aware that the pot of gold is just an illusion, especially for him. If he only wants the career for money, you should save your money (I assume he wants dad to help with the financial end of pilot training). If he wants to be a pilot, no matter the level and doesn't mind if he never reaches left seat of a 777, he will have to work harder than most (and most already work danged hard); but he should be able to have a fulfilling career.
Good Luck