I think it really depends on the state/province you live in and how it's regulated. Additionally, I also think it depends on the organization you choose (or are able) to fight-in.
Check out who regulates your state/provincial MMA and which leagues would be available for you to fight in. You can search this on google or if you train I'm sure your teachers and other students would be able to provide you with the info.
If you can't compete at the amateur level yet, I would recommend competing at various tournaments (BJJ, muay thai, etc). This will allow you to get a sense of what it's like to compete at a higher level, become more experienced at it, and can lead to amateur fights when your of age.