First, what is your passion? Is there is something that you really enjoy doing such as taking pictures, making jewelry, or designing clothes? Or is there a service your neighbors and family members are willing to pay you to do such as yard work, running errands, or teaching them to use a computer?
If so, then you can turn your talents and skills into a business. You'll need a plan that describes what type of business you are going to have, who is going to buy what you are selling, how much will it cost you to make and how much you will sell it for, and how much time you have to invest in this business. A helpful idea is to find a mentor, an existing business owner, who will help guide you through the process and be there to answer questions about your business.
There are a lot of great resources out there to guide you through this planning phase. To get started, check out SBA's Teen Business Page.
