Age doesn't necessarily matter. People are like wine, they just get better with age. There is no greater joy than to "being your own boss". There are a lot of other factors to be considered before starting a business( http://www.aspirefcu.org/blog/life-advice/starting-own-business/ ), than worrying about age. If you have a solid concept and the will and energy to work towards it, then no matter what, you will be successful in any age.
Age is just a number. What matters is your ability to pull yourself up and run after the goal. If you can do it best at 60, then that's the right age for you to startup.