I got into real estate when i was 33 and have been full time every since. If i would have known what I know now, I would have became a real estate a lot sooner.
However, working for Fortune 100 companies provided me valuable training, experience and the importance of being a professional.
At 18, i would wait.. if real estate interest you, find broker you can respect and emmulate.. Have him show what it mean to be a real estate agent. You might prefer being a sales rep for title company or another vendor.. for sure it will open doors if you get in sooner than later...
My broker started when he was 24... 24 years later... he still looks like he graduated high school..