You are 20 and afraid it might be too late to pursue a career as a historian What would you need to study Where would you start?

If it's what you want, don't let a couple of years stop you. I started a degree at 26 and I'm glad I did.

Decide what you want to study history for - do you want to teach it? If so, at what level (grade school, high-school, college?)as your qualification requirements will differ.