It's just that, when I was 18 - and a friend and I had finished college (All IT related) and thought we were ready to take on the world. We messed around with starting up an IT business but, naturally, ended up doing the usual shitty home user stuff like cleaning viruses and installing new hardware.
I then went and got a job doing 1st / 2nd line support for a school where I really began to learn. Business IT is a long long long way away from whatever you can do at home or in school / college etc. Trust me on that - get some real world experience first!