Things to think about

When I was in year 5 of this business, I took a class through the Small Business Development Center called New Venture Training. It was a class designed for those contemplating owning a business/growing a business and we all wrote our Business Plans. The class was great fun, we learned alot and got to bounce ideas off each other, I can't recommend it highly enough. They do have some scholarships available and I do encourage you to look into it.
They also had a financial class that went along with it, that was 4 sessions I believe. Anyhow, the ONLY thing I took exception with, was the instructor said "if you arent perfectly healthy, if you even take an aspirin now and then, being self-employed isn't for you". I think if you have any major health issues you need to give a little extra thought to how you'll work around the issue, but I wouldn't let it stop me!
I think the main thing is to know that if you do decide to go into business, it will require dedication and sometimes even sacrifice. You will need to have great self-discipline, it all falls on your shoulders. But the thing is, for me anyhow, the rewards FAR outweigh the challenges. and remember "Nothing is impossible to a valiant heart" :-)