I think you're underestimating your market.  First of all, your spelling and grammar needs improvement.  I don't know how many times I've found a sweet deal on some part for my computer and decided against buying it because the website had all kinds of spelling errors.  It may seem trivial to you, but attention to detail inspires confidence in the buyer.  If you can't take the time to learn how to spell correctly, how can someone expect you to take the time to service their computer correctly?
Also, most people who don't know much about computers get some type of warranty with their computer so when something goes wrong, they can have it fixed.   If you expect to have a snowballs chance in hell of surviving, you need to have a nice store front, certifications on the walls, and be prepared to offer a warranty on anything you replace/fix -- and you better be prepared for people to milk those warranties for all they're worth.  You need funding, so unless your parents are rich that means you need a business plan to get some grants, and someone who's willing to co-sign on loans for any other funds you need.  You will need to have backup parts for pretty much everything, meaning EDO ram, PC100, 133, DDR 2100, etc etc.  You'll need lots of miscellaneous cables, different size power supplies, a nice stockpile of network cards, modems, CD-ROM drives, hard drives, video cards, and a couple motherboards and processors laying around.   You'll need a nice clean work area, tools, anti-static bags out the yin-yang, and a couple monitors and keyboards/mice or a nice sized KVM switch.
I'm not trying to insult you or your abilities, since it's obvious that you're young.  We were all young once, and it is good to have ideas and even follow through on them sometimes.  However, the people who go far in life are the ones who plan, plan, and do some more planning, and work their way up from the bottom.   I think you would be better off to start studying for some certification tests, maybe try and get a part-time job at a local ISP or something and get some hands-on experience under your belt.  You would be surprised how 'average' people who don't know much about computers have a knack for screwing things up to the point of baffling even the most experienced techs.  Most 'average' people save important things on their hard drives, have no idea what the word BACKUP means, and don't just want you to reformat and reinstall Windows for them.   Most 'average' people, even after you fix their problem, will have no idea what they did wrong and will probbably do it again, but expect you to fix it for free the next time.  Unless you are fully prepared to deal with every situation that might crop up in a cost-effective manner, you will just end up losing money.