Happiness.

I'm breeding my own feeders, and by selling excess I pay for the food and bedding. So the only thing I'm giving is time, which I"m happy to do. I like raising rodents.

I've currently got 4 snakes. They eat 2 fuzzies, 2 hoppers, 1 small mouse and 1 small rat, total each week.

I have 1.8 mice, 2 females per tub, the male rotates every two weeks. And 2.2 rats.
Production is 2 litters of mice every 2 weeks. Which is way more than I need if you do the math. And I figure I'll get 2 litters of rats every 12 weeks, my female rats are prego for the first time right now so I'm guesstimating time frames. My bp eats f/t so 2 litters frozen at the right size will last till the next 2 litters are ready.

I've got one person who buys all my excess at a dollar a mouse and in the future 2-3 dollars a rat. At least 10 dollars worth a month which covers my consumables since I buy bedding and lab blocks in bulk.

True my initial setup cost me and it took me a long time to find someone willing to buy in bulk from me, but I'm really happy with how it's working out now.