With only two snakes I say don't even bother at this point. The biggest issue with raising rats is that you're going to end up spending most of your time on them instead of your snakes just because rats require much more daily maintenance and care (don't go mice, mice stink in every way). There's also the associated costs, which you'll find is about the same as if you were to buy frozen. Rats eat a good bit and you'll be throwing out half your food supply if you don't have a rack or a hopper system since they like to bury it in their bedding. Once you get more snakes (if that's your plan) then by all means reconsider, but for now I just wouldn't.

You can always get a single rat and raise it for a while to see if you'll enjoy/tolerate rat keeping? I personally prefer to buy younger females and raise them to a good breeding size anyway, I've only ever had poor luck buying older females that were already up to size (four pups from one! Four!).