you might want to breed other things other than fish alone.. maybe snakes/lizards, those can fetch high bucks
or create large indoor ponds in the basement and start importing Arapima Gigas (like that guy in Amazone got these Ara Farm) and introduce it as commerical fish to your local markets and maybe stick a few high end king arowana in it
You gotta consider breeding fish is not a necessarity in life.. so you wont have a fix income unless you can sell a large quantity
THINK ABOUT IT! If this was so easy.. (under $5000 to set up/work less than 3 hrs a day/make at least $1500 a month) we wouldve done it already, but then again.. if all of us did it.. Crazy competition xD and in the end it wouldnt work at all xD