First, I just want to let you know that there is no reason to be so defensive. Boo wasn't trying to imply that you weren't going to be a responsible dog owner at all. She was simply stating that a new owner asking the questions you were asking is a pretty common occurence. These situations rarely turn out for the good of the dog and often lead to dogs been given to friends or dumped at shelters.
No one is saying that this is what is going to happen if you get a pup. However they are saying that if it doesn't happen then you are the exception not the norm. No one here knows you personally so opinions can only be made by the information that you give us.
Pitbulls are very people oriented and really need a lot of attention compaired to other breeds. A happy pitbull is one that is with his family as much as possible. I myself would not keep one outside for this reason alone. A pitbull requires a great deal of love and attention and you can probably double or triple the need of one that is an outside dog. They thrive on the love that you show them, and often do not do well without it. A pitbull gives you its undevided attention and should recieve the same in return. It makes for a much better dog/owner relationship.
Have you talked to you parents about getting a pitbull? What do they think about them as a breed? Are they willing to care for the dog if for some reason you were not able to?