Ok, first things first, following up on my first post (which doesn't seem to have arrived). You CAN do it in a 5gal tank. But it is certainly more difficult and challenging. Males and females can tear eachother up until they die (my one female did that to my prize male the last time I bred them, and I had them in 10gals. Second of all, MN_Rebel, I would like to address that it was very rude of you to comment on the maturity of gar man, I am in High school myself and I have sucessfully kept 10 tanks, and have bred bettas successfully. Maturity comes not with age or with education, but experience. I am sorry if I am out of place, but I have seen this kind of nastiness on other forums and if this is what must be expected then I wonder at my decision to join.
Now, Gar man, it is difficult to house possibly 200 plus bettas. And even if you donated them remember that not everyone will get one right away. The best idea I can think of is set up a website and establish a steady breeding/selling program. It will take you several tries to get it right, probably, but once you get going it will even out. Remember that you can make money off of them, and you want to be able to provide for your bettas when you move out.