I think that many teenagers are very interested in becoming a camp counselor and I think it's important to give them a opportunity to learn some leadership skills and how it everything works behind the scenes at camp. I've found that many camps charge full or reduced tuition for their CIT programs but I think it's a better idea to offer a free program that has a very selective application process. This way you can get a diverse group of kids and maybe even some kids who have never been able to afford camp or specifically your camp if it's expensive. Keep the group small so you don't have a huge group of kids not being able to get a job the following summer. The smaller the group the more the teens will get out of the experience and they'll be better counselors. Make sure your CIT group gets to spend some time together to bond as a group. Often 15 yr olds are a good age group for this because many teens need to start making money at age 16 so they can contribute to paying for college or buying a car.
Hope this helps!