I'm a bit more picky about my rats, and only keep 3 females per 24"x32" cement mixing tubs. Sometimes 4. A 10g is way too small even for one. Besides, then you have to put the water bottle in the tank, where it can get chewed up. Then you have a watery mess on your hands.
Are you sure you want 2.12? That is a LOT of rats for 6 snakes, you can sell the excess if you're lucky enough to find buyers. My 2.11 colony has left me with a ton of excess in the freezer. It is also a LOT more smell. Do you have a well-ventilated area? Tanks are pretty poor for ventilation. Ventilation problems can lead to RI, just like in snakes.
Daily care is needed for the rats, whether it's providing food or water (they go through a LOT of water) or keeping their cage fresh, as well as checking to see if they're healthy. If they become ill it's still your responsibility. I highly believe there are quite a lot of breeders who only do it for their snakes that really shouldn't be. Rats are not to be treated like some people like to treat them, they are still intelligent animals that crave attention and stimulation.
My 4 tub rack (with 24"x32" large cement tubs) cost me only about $120 including the tubs. I would recommend doing this, it was actually a lot of fun to build!
I used this plan, except for the main frame I used 2x4s instead of 2x2s.
http://www.rodentracks.com/Large-Tub-Rat-Rack.html
Here's mine
Breeding rats is very exciting and rewarding to those who love them, as well as being somewhat cheaper per rat to produce your own.
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