I am also pondering this question as my collection grows...

What would be the best way to estimate the cost of breeding rats to see if it's cheaper then buying them?

I know you would have to buy them housing and auto water equip(should I choose that) but that is just an initial investment that won't be factored into the monthly expense.

But after that, you need beeding and food. I think that's it, am I missing anything? So how much beeding and food would you need per month??