Rats have a litter once every 20-25 days with 23 being average. Pretty much once a month. Litter size can vary but the average is between 12-18. A good quality food for rats is Mazuri lab rat chow that is designed especially for breeding rats. Purina Mills also has rat diets (in fact I think they also make the Mazuri lab chow as well). These are fully balanced diets made especially for rats. Others just use dog food that contains no dyes or preservatives. What to look for is high protien (21% or more) and fat around 8%.
For the amount of snakes you have, you should have one to two 1:3 colonies of rats, this way you can freeze the excess for lean months or sell the extra to help cover the cost of food for the rats.
For containers, alot here use the large mixing pans found at Home Depot. I use the large rubbermaid roughneck tubs that are about 151L or so.