I keep a 30gal guppy tank that was giving me about 20 juvenile males a month to sell. Of course once I hit that point, I sold off everything but the best looking males. Just be prepared for a second tank to use as a growout tank if you are actually interested in pursuing line breeding. I suppose you could also divide the tank and keep less fish overall.
I may be interested in some traits if you wouldn't mind listing some? Or even just saving some of your fish from being food! I do use guppies as feeders, but only deformed ones, and that goes for all fish I breed! lol
And are the guppies in with a male betta? Are they adult guppies or juvies? Juveniles will shred the betta's fins a lot faster, but adults do nip it down over time as well.