There are dog training schools, and if it's something that you truly want to do I would start now.
At least start off as an assistant or intern or the like. At least ask a reputable trainer in your area if you can sit in on classes because you would like all the experience you can get because that is what you want to do.

In order to really make a good $ out of it you need to be reputable, have refferals so like I said start AS EARLY as possible, start building up your knowledge & clientell now.
It is also a good idea to do the same with area breeders & local shows (even if it isn't obedience), a good trainer that makes money knows everything about every breed, all obedience commands (hand & vocal), knows all aspects of obedience showing, how breeders work & so on.

Good luck!