Hi, J.,
I have not put my kids in modeling or acting, but my husband has worked in the entertainment business for several years and some of my friends have put their kids in modeling and acting. Based on what I've observed, for the vast majority of families, the amount of work involved for both parent and child makes modeling/acting not a very cost-effective way to save money for a child's college fund. (I think that most people would save more money for their kids by working (the adults working) and putting some of their earnings into a 529 account.) I would only do it if my kids expressed a strong interest in pursuing this activity as a job.
If you and your son are serious about this business, then you need to create a portfolio, which includes photos and a resume. As already mentioned, your son needs to get a work permit. All the kids I know who work in this business have at least one agent. You probably need to be free to take your son anywhere on a moment's notice at least a few days per week for auditions. Classes in acting, modeling, dance, gymnastics, martial arts, singing, etc. are considered desirable. To make it in this business, I think that it helps to be "a crazy stage mom." That's another reason I have not tried to get my kids into the entertainment business.
Sincerely,
Lynne E