[FredWolfLeonardo]

I imagine alot of their food comes from dumpster waste and food thrown down the sewers. (although in versions such as the OT, they are shown to buy pizza and have money, but before that they most likely accquired the taste of the stuff after picking up pizzas thrown away by Viny's pizza for not having the correct ingredients or something)

As to where they get their money from, I don't think many versions of them used money at all or needed it since many items in the lair could've just been acquired from the local dump and food is pretty readily available in the city, even for the peniless. When they did need money in the OT and were out, they did work jobs rather than ask April.