A typical person's brain does not even become fully formed and wired until their early/mid 20's. At 18 I would suggest opening oneself up to all the possibilities -- college is good for that, especially if one is not self-motivated to experiment and study.

If one KNOWS that one wants to be a pro photographer, then go for it. But if one just thinks that photography would be an interesting way to earn a living, then keep one's eyes open to the whole world of possibilities.