I started in the fire service when I was 16 as a volunteer, Im 49 now with 25 years in a career department. I personally couldn't imagine having any other job. There is a great feeling of satisfaction knowing you did your job well and made things better for someone else, but it doesn't always work that way and seeing bad outcomes can really eat at you over time. Most of the calls you will run will not be filled with excitement, as the other guys have stated. The job takes a toll on your body too. Bad back, aching joints, it can be emotionally draining, definite high risk for cancers as was stated.
Most departments don't have fantastic pay, but the benefits and retirement can be pretty good- definitely look at what they offer. Im very fortunate to work a 24 on / 72 off schedule, 1 mandatory day off every quarter plus leave time earned.... definitely great for hunting and fishing.
If you do decide to get in, always remember that your life, your crew's life and the public's life are in your hands.
Take it seriously. Learn the job and know you'll learn something everyday.