You don’t make profit off of guppies and it’s hard enough to BREAK EVEN when breeding fish let alone make a profit. I wouldn’t bother trying to make a profit.
Well you can make profit off of guppies but to do so you either have to breed the REALLY nice guppies which cost a lot, develop your own strain which takes years and lots of money, or breed in bulk which takes time, money, and space. And the amount of space it would take to make it profitable would be more space than your bedroom.
The only real way to be profitable would be to breed marine fish I would imagine but don’t even think about it.