Computer business worth it?

I'm 21 years old and did an AS level in IT communication, which didn't teach me anything about repairing software or hardware on computers but since have gained knowledge and interest on it, I would like to offer a service in which i do this and hopefully make it lead towards a business. I just wanted to find out how much you really need to know about fixing them, it comes quite natural to me but most people would say it. Any pointers?