It's very hard to turn a profit. Even if you're very good at it, and determined it will be years before you have the right number of morphs to make enough, and you'd still have to pay for fresh water every day, rats/mice, and heating of course. Even with all that, they're animals and not to be predictable. They don't always breed when you want, or produce the amount you hoped for.
Then there is vet costs if one were to get sick.

It's not an easy way to earn a living, and even the ones who make a living off it, usually don't make big bucks or have side-jobs or partners with side-jobs.


Now, I'd recommend having a couple as pets, if you really love them...But if you plan on going into a business expect a lot of hardship.