The problem with reptiles (or any animals for that matter) is that so much is out of your control. Maybe a female lays a bunch of slugs, maybe you hit terrible odds and only get one morph in a clutch of 12, maybe a powerhouse male you bought (eg a $5k investment) isn't interested in breeding, etc, etc.
There are so many variables that IMO, until you really get up to a very large scale where you can absorb those variables, it's going to hard to consistently make a profit. I've had a couple of years where I had incredible odds (eg het x het gave me 6 visuals out of 7 eggs) where I had many more valuable animals to sell that I ended up in the black for that year. But those are far and few between. Most years I'm in the red, but that's OK with me. I do this for fun because I enjoy it, not for money.
I think if you go into it trying to make money, or expecting to make money, you're going to be very very disappointed. I always tell people to go into this as you would any other hobby and that's essentially as a money pit. Don't "invest" with the intent of making that money back, because you likely won't.