Yeah, good plan from trucky. You could also consider buying off aquabid if you were serious, but the price of aquabid fish usually means that they are only imported by serious breeders. There are members of this site in the UK who breed bettas and will ship within the UK for very reasonable rates (bronzecat + netty, modaz who runs dpfishways come to mind, but there are too many others to list. Keep away from somebody called Jaded12 who agrees to sell bettas and then fails to send them - and insults anybody who tells her that this is unfair, invariably causing flame wars.)
If you did want to breed, keeping the pair permanently in a divided tank is not a good idea. The male will get used to the idea that the female is there and he cannot get to her, and so will not be particularly interested when you try to breed them. Also the female can get so overexcited by having a male next door that she ends up eggbound. It's best to keep them and condition them separately and only introduce them a day before you plan to let them at each other. This is enough time for the average male to build a bubblenest.
And yeah, you could end up with 300 baby bettas. That's 150 baby males. That's 150 jars, plus 40 gals MINIMUM of female growout tanks to water change. Every day. (AND three hundred mouths to feed.) So it's not something you should do unless you definitely have the time and the money. Of course you don't have to raise all three hundred. You can remove some of the eggs or some of the fry. But you're looking at $100 whether you raise 5 or 100, and then a fair bit more if you're going to attempt to raise the lot. The hardest bit though, IMO, would be finding homes - decent homes, not torture-chamber-tiny-cup homes - for 300 young bettas.
It's really rewarding though, and something I'm definitely going for - but only one pair at a time thanks!
