Id use a small wire cage used off craigslist if i was you and get the Lab Block at Tractor Supply Plus or Country Max ect.. (25lb for $19.99). A bag of that will last 2 years if only feeding a couple rats.. Then get a glass water bottle so they dont chew it or youll have a mess.
With all this said, your not going to like doing this i dont think. Mice stink Awful after only a few hours and Rats are great but will grow to big within a month. I Breed ASF's because of No Smell and they dont grow fast at all but you cant get them at Pet Stores.. Before you spend a lot on this project try it for a week with what you have. You might change your mind quick when you smell that stink off the mice when you come home from work hahahahaha
Ps- any dog food that isn't colored is ok for the time youll have them until you find Lab Block.