Of course it's ideal to start training competatively at a young age but if you wanna learn and you think that you've got the dedication to fight proffesionally, why not?
The most important thing IMO is conditioning. You can learn alot of what there is to know about MMA and the basics in about 4-5 years and coupled with extremely good cardio you could be fighting in competitions in less than 2 years.
And as for the fear reflexes, get yourself in a club with lots of members and make sure that they spar at an easy pace that suits beginners. Only countless hours of sparring can take away the bodies natural reflexes.
Also, I would try to find a gym/club that teahces all aspects of MMA or maybe a Vale Tudo club. If that isn't an option i would picik Muay Thai over Kick-Boxing as it teaches you to fully utilise the clinch, elbows and kness.
Overall, if you want to compete proffessianlly, you need to dedicate pretty much your whole life to training. it's just a matter of how far you're willing to go and how much you're willing to work.
Edit: Checking kicks is a lot harder than it sounds. But it all comes with practice, it's not something that you can learn overnight.
Last edited by T.Bone; 09-28-2009 at 06:36 AM.