First thing: I am 20 years old... I bought my busa when I was 18 and had it for about 2 years. Now I sold it and got a Gsxr 1000.
Second thing: I know what I'm doing on bikes... ON THE BUSA, I was doing burnouts, moving burnouts, wheelies, stand-up wheelies, stoppies, and I topped it out a few times... some stock so I could see it top out at 186 and some with the TRE to go 190+ .... I also drag-raced the busa at the track... The reason I am saying this is so that you understand that I have experience and am skilled with bikes.
Third thing: I dropped my busa making a simple 10mph right turn... The busa is NOT forgiving... I wasn't paying enough attention and I guess I gave it too much throttle when I was turning (and by too much I just mean a hair... I wasn't trying to race... I was just making a turn into my development where I live...) Anyway, the rear wheel spun out from under me... .... I have enough throttle control that I can balance the bike on one wheel and wheelie for a very very long time.... yet, the busa bit my a$$ on a stupid right hand turn...
Last thing: It IS possible to learn on a busa... although as you can see, not very recommended. I think you really want the bike because it's cool, fast, comfortable, etc, but inside, you know the answer to your question. The reason you're asking whether you should get the busa or not is because inside, something's telling you that you shouldnt do it, however you are looking for someone to say "i learned to ride on a busa, and I was fine" to make you feel more confident about getting your "dream bike". A million people could say "dont do it" but you will just focus on the one person that said, "do it"... In the end, it's your life, and you have to decide... we can't tell you what you can or cannot do with your money. We can only pass down to you what we've learned from personal experience. If you are new to riding, ANY bike will feel VERY fast and VERY fun. I promise. I have a buddy of mine riding a 2003 Ninja 500 and he's loving it. He is looking to upgrade to an R6 in a month or two.