Ok, for 2 snakes that should be easy then.
One or two female rats + male.

If you have 2 or 3 stackable tubs/rack, that should save space.
1 tub for females, 1 tub for the male (if you want to keep him separate), and 1 for grow outs. You could combine the male and grow out tub if you want. I sometimes do that.

You can use kiln dried pine bedding or pine pelleted bedding. They're both pretty cheap($4-7/large bag) and will last you a long time.
Both are good for keeping odors down and is absorbent.

A few drops of vanilla extract into their water, good air circulation, quality diet, and cleaning up at least once a week will keep odors down.