Our neighbor's DS enlisted, had the grades to go to college, but he decided he wanted to enlist. Ironically, his parents were completely opposed to this, because Dad was enlisted, and later on became an officer via OCS. It took the Dad about 6 yrs to get into OCS, he never tried for the AFA.
DS applied about 16 mos in, got Commander support, but did not get AFA. For him this actually created a new problem. The next summer he started up the paperwork again, BUT the Commander told him NO this time. The Commander felt that he had his shot and the AFA did not accept him, so he was giving the shot to the next guy.
This would be how any Commander would see a promotion board for an officer, if they gave a DP or P and you didn't get it, they are not going to give you that again.
He is finishing up his college degree using TA, and now is in the process for the OCS board. The problem is now the AF is downsizing, so that is not a guarantee.
Nobody can project the numbers in the future. I agree if he wants to serve and is happy going enlisted, than he should.
This is just my personal advice and throw it in the circular filing cabinet when done. Pull the DFAS pay chart, sit down with him and work the monthly numbers for him as an enlisted. Pull up cell phone, car insurance, car pmts, gas, etc. to illustrate that if this is the route, he must be sure since there is no guarantee he will get into the AFA or OCS. He has to want to be enlisted.
He can't do this just as youthful exuberance.
Good luck