From my experience the rats dont breed like rabbits. I have two female rats in with a boy for three months and just got a litter from both of them a couple of days ago so. But if you do decide to breed your own feeders, i would definately recommend that you get a rat rack. It makes everything a thousand times easier(compared to 10 gallon glass cages). And go to your local feed store and they will most likely sell 50 lbs bags of lab rat feed(was $20 at mine) and get that it is way cheaper than anything that petco sells. But yeah for 4 snakes i would not breed rats, maybe when you hit 5 try it out with two females and a boy and see how you like it. If you absolutely hate it you can stop.