I'm sorry but I find this very inappropriate. You definitely should not be studding pet store rat's out and any reputable breeders will certainly take no interest in it. Do you know what lines these rats come from? Do you know the genetics and health of their parents and grandparents? Do they have pedigrees? Do you know what kind of temperament their parents had? Breeding isn't something to play around with, there can be a LOT of complications and doing it right can be quite costly. Please think again before creating more homeless rats, and instead maybe urge people to adopt rescues who need those homes more.
If you do want to become a responsible breeder you need to find a mentor (another reputable breeder who has been breeding for a few years and follows general guidelines and ethics) and start with healthy breeder stock NOT rats from pet stores and mills. I hope I made that somewhat clear, let me know if you have any questions ^^