The only thing that keeps me from getting a ton of bettas is the water changes. And the setting up of new tanks haha. I dont like it. I have another 3 gal so I will be getting one more betta. I'm going to stop at 2 though
Im also not sure its really a business - first time round prob definately not ! food tanks extra heat mats extra tubs that kind of thing is expensive ! also if your stuck for room already where are you going to put the whole seperate tank you will need for a grow out which will be 12 gals plus ideally (this is a completely different tank to the parents tank) You would also need a large jar with air stone and heater if you wanted to culture brine shrimp for the fry. Decapsulated brine shrimp eggs cost 5 pounds a bottle.
Also if your at college are you there permanently if you go home in the holidays its not the best plan - my betta babies were born early january and a couple of weeks ago my landlord told me I had to move into temp accommodation because my bedroom had structural problems in the ceiling - so I had to move 26 babies roughly 3 adults all in individual bags and jars in my car! it was a nightmare!
Netty's website tells you all you need to know but these are things to consider, if you choose to breed do a lot of reading and research and give it a few months before you decide, then everyone here is happy to help