it depends on how large you go.
when i started, i went with one family.
i paid $4 for a rubbermaid tub, $3 for a water bottle (melted a hole in the side of the tub and fed the metal part of the bottle through it to prevent climbing). at the time i used pine, which i had for my snakes anyway, but a nice size bag is about $3. i bought them lab-style food pellets for about $4. the mice themselves (3 females, 1 male) were a total of $4.
the total cost was about $18. one female was pregnant. she had 10 babies. my agama got two before the male cannibalized the others. the second one to have babies had 4. 2 were used as feeders, but on xmas eve my cat sabotaged my mouse breeding project, eating the 4 adults and both remaining babies.
my next plan is to go with a rubbermaid plastic drawer system (about $10) to hold 3 seperate families.
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currently have:
blue tongue skink (skinky),
pygmy rattlesnake (gordon),
nile monitor (dick),
reticulated python (mousetrap),
egyptian painted agama (george),
ball python (snake'n'bake),
red-sided skink (skinky jr.)
mozambique spitting cobra (fluffy).