Hey StavroulaG,
Go for it! Don't let anybody stand in your way. I started at 15 and didnt have any problems except for lack of experience and failing at my first few ventures but then that was my business education
Obviously as said before, you probably can't borrow money and things like that but you are better off not doing that anyway, until you have a good idea of what you are doing.
What business are you going into?