Well, mine are in my living room. Anywhere else would probably be a better arrangement. Some people have their own rodent rooms or a rodent/snake room. I think eventually I'd like to weatherproof a shed for my rodents, or maybe use a garage if my next place has one. Looking to move this coming year.
...that sure is a lot of math. The most I've ever had in one tub was 35 babies and their 3 mothers, so 38 total. Once they got to weaned size it was too crowded and I had to split them up. The bigger they get the less you'll want to keep per tub.
12 tubs is a lot of space, but the upper end of your calculations is more than they can handle. The thing is though, you can always slow down breeding when you have too many or speed it up when production is low. That's one of the many benefits of rotating the males in and out of the tubs instead of keeping them constantly in with the same girls.
Right now, since you only have 13 snakes, you could plan to produce 1-2 litters/week and then work your way up from there. It'll give you a good feel for how fast they grow. Then if/when you get retics you'll only be holding back enough rats to feed the two of them. It's going to be a small precentage of your total feeders. It helps to keep a tab on the numbers. Count all the snakes you own and think of what size rodent each of them will need. If you end up with, say 15 adult ball pythons and 2 retics, then you'll only need to hold onto 2 out of every 17 baby rats you produce for more than a month.
I'm afraid that's as much a help as I can be. I hope some of the other commenters/forum goers will chime in if they have experience raising rats for larger snakes.