Hiya Timmy!

I had a side hobby of fixing computers when I was in high school. I had always tinkered around w/ my comps, built a few (I started in PC towers which are a lot easier to work with than laptops) and maintained them in healthy condition. Most of my family and friends knew I was good at fixing comps and would ask me for help.

Through word of mouth I had friends of friends ask me to do simple things like upgrade ram, install a new hard drive or to fix the general problem of "it runs slower." I generally charged "whatever they thought fair" which sometimes was a lot and sometimes was just lunch. I was more interested in playing w/ electronics and helping other people than making much money off of it.

I'd recommend learning to fix "computers" and "electronics" instead of just "macs" and "ipods" because they're pretty similar and experience in one will help with the others.

One of the first questions you have to ask yourself is, "Do I know what I'm doing?" Have you messed around with hardware before? Replaced RAM? Installed a new Video Card? An OS from scratch? Scanned for viruses or spyware?

I'd say you need experience in all of those things before your going to be of any use as a technician. I recommend starting on PC's because they're much easier to work on, get parts for and PC technicians are way more in demand.

Depending on where you live getting cheap parts may be easy or very difficult. I'd recommend Craig's list. You can also try contacting a local electronics recycling place and see if they're willing to give you things people throw out (you can find some amazing parts in other people's "trash"). Look for any cheap/free electronics. Swap parts and try to fix them if they are broken. Put together the fastest machine you can. You can sell the comps you fix or (what I did) give them away to charity. My high-school also had a class in Computer Repair where we butchered and assembled comps which was a lot of fun.

If you want to make a "business" you have to build up a reputation. At 13 people aren't going to trust you with their expensive electronics unless they know you or know someone who you have helped. "Advertising" will get you nowhere but being friendly and helpful to your grandparents (or people that age) will give you tons of business.

In summary, learn to fix computers on your own and offer to help other people with their computer problems. If your nice and useful you'll find the business finds you ;)