Gosh, I hadn't seen this thread before now.
Breeding, wow. I had no idea you were planning on that. That's a big undertaking.
I would gently suggest that you not do it though. There's several reasons why.
One, you don't know their genetic background. Pet store rats are a big what if. 90 percent of them come from horrible rat mills, where they are bred primarily for looks so they'll be pretty and catch people's eye. Most of them are prone to tumors (not something you'd want to deliberately breed or be able to anticipate as most tumors start appearing well after safe breeding age), weak immune systems (prone to myco flare ups and other respiratory issues), and are not specifically bred for good temperaments (making breeding a risky venture for future hormonal aggression, fearfulness etc.).
Two, because they are so easy to breed, that is the very reason they probably shouldn't be bred. There is already an insane overpopulation of unwanted pet rats. Rats are among the more expensive pocket pets to keep humanely because of their fragile immune systems, so it's hard to find good homes for them.
Three: Well, three...AFRMA says it better than I can, and addresses all the other hesitations I would have for breeding rats so I'll just post their article on the subject here:
Because you seem to be sharing various hesitations on aspects of keeping your rats, I'd humbly suggest that you'd be much better off and I honestly think happier in the end to NOT breed your kiddies. And you'd spend much less money, time, and stress just to spay your female and put her in with the boys, choosing to buy a new rat or three when you want another one.