What are usually the prerequisites for these types of jobs?
For IT jobs? Although there are some exceptions, most employers just want someone that's willing and able to do the job they're advertising at a rate they can afford to pay.
The question you need to ask yourself is how you can convince an employer that you're capable of doing the job. Enough people exaggerate or outright lie on their resume that an employer isn't going to take your word for it; they want to see verifiable experience and/or certification by a trusted party (an educational institute, a vendor, etc.) that you have the knowledge needed to be successful on the job.
If you resume is good enough to get an interview, you then need to convince the employer that you know what you're talking about and that you can solve their problems.
Based on your post, it doesn't look like you have any relevant experience or degrees/certificates, and it doesn't look like you know anybody that can put in a good word for you. Employers, especially in this economy, get so many resumes from candidates as equally (un)qualified as you that they'll look at your resume for a few seconds and then just throw it in the trash. In the unlikely event that you do get an interview, phrases like "I'm good with computers" or "I want to work with computers" won't inspire much confidence in your skills.
If you don't want to go into debt for a bachelor's degree, I strongly recommended going to a community college and getting an associate's degree, or at least going through their computer science program. It's not expensive, and the credentials you'll receive from the college will help establish your credibility in the field. You may even have an opportunity to gain some experience with an internship. In addition, many community college professors that teach vocational subjects actually work in the industry, and they may be able to get your foot in the door if you impress them.
Once you've broken into the industry, you can move up quite quickly if you kick ass and impress your employer. You'll probably reach a point where you can't really advance without more education, but by that time, you'll have a better idea of whether pursuing said education is worthwhile.
Edit: BTW, many of the courses that you take at a community college will count towards course requirements for a four-year university. If you get an associate's degree and then later decide to pursue further education, you won't have to start at the bottom.