Hi
Age shouldn't matter with anything, but it will help if you are over 18. If you have a passion and desire to start your own business and the skills (or know someone with skills that can help you), nothing should stop you. Don't take 'no' for an answer. Keep trying until you get a 'yes' from someone willing to help you get started.
Do as much research as you can on your competition, your costs, the required experience. Government websites have so much information available for you to read.
If you can show you understand about how business works and how you can make 'your' business work, you will have a much better chance of being heard.
Best of luck
Michelle