The best free application that I can remember and would recommend is LMMS
Reaper is affordable and pretty damn good!
As you can see on the purchase page there are two licenses, you would most likely qualify for the discounted rate of $60 which you can still use for commercial use! Read the panel to the left on the licensing page =]
Fruity Loops is another that I have used a lot but I no longer have access to it =\ it's not too expensive from what I remember, I will be purchasing a license of my own soon enough I think :P