my friend had 12 rats in addition to the tons of other pets she had. She only bought 2 rats at first (both female) but one of them had babies like right after she got them. I think shes going to get rid of all but one of them though because the one that had the babies (and all the babies) are feeders and they're kind of sickly and she doesnt want the rest of her animals to get sick. and they arent very nice (except the one shes keeping).