First off, welcome to BHQ buddy. That's bad ass that your only 13 and trying to figure out ways to get your first banshee, don't give up and you'll have one before you know it!
X2 on starting to save every penny you have... that will help alot. Maybe find a decent job and see if a family member will co-sign for a loan on a used banshee? You could get a decent banshee at a pretty cheap monthy payment IMO. Or work your ass off and save for a few years and pay cash for one.
Good luck, let us know how it goes.
-Zach