First thing about betta breeding. They will have between 50-200 fry! Not all these fry will survive, but you need to be able to plan on homes for all of them. Another thing. The male bettas will eventually start showing aggression towards one another. You will have to remove each into his own container.
The actual breeding process will cost some money. You will need a ten gallon tank, sponge filter, air pump, styrafoam cup, heater, light, water conditioner and of course 2 bettas. that could cost anywhere from completely free (due to your current supplies) or $50+. So that means if you do not sell your bettas for more than the start up cost, you could actually LOSE MONEY. and no one wants that to happen. Although breeding them is fun. You can give it a try if you want.