Average guy... Im a professional firefighter/paramedic in Illinois. I can tell you that it is the GREATEST job in the world. Getting hired is like hitting the lottery. I was a soldier and worked in law enforcement before before becoming a fireman and there are times that I look back and wish someone would have told me abount this profession at your age (i was 31 at date of hire).
My advice to you at your age is to see if any departments around you have an explorer program you can participate in (its like being a junior firefighter). See if there are any volunteer departments around you that you can work with. The time commitment is usually reasonable and when interviewing for a paid department i think it says something that you volunteered your time for free.
Also go to your local fire station and talk to the guys. See what the job entails, ask their advice. Call every human resorce dept. of every city you may want to work and ask for a testing packet(then you will know the qualifications). Hope this helps.
Any other questions, just ask. P.S. my hiring steps were 1. make it through the hiring process (only 19 out of 400 passed every step)2. complete fire academy and emt school 3. make it through my year of being a probie (get badge). 4. Get paramedic license(3 semesters of college and clinical time).