I know a woman who rescues cats and keeps up to 30 at her large house. I have been there and she keeps it very clean, but goes through tons of kitty litter and food. There are also vet bills when they get sick or she finds a cat which needs to be seen to get shots etc.
Add to that the travel of transferring cats to a good home and she spends a lot of her own money. She is older and lives on a fixed income which makes money tight.
We have two cats from this remarkable woman as she said she had sisters who needed a good home. As I type this, one kitty is on my bed in her nest happy as a kitty clam!
We need more people like her in this world.