Keeping a cat inside means teaching it to use a litter box. While you may think you just need to fill a litter box with litter and everything should work out all right, that’s not always the case. You have different types of litter to choose and different type of litter boxes to buy. All of this means that you may need to take time until you find the right litter box and litter that you cat will actually use.
Some cats prefer covered litter boxes while others do not. You may also need at least one litter box per cat so that way cats don’t have to fight for the litter box. Also once you find a brand of litter your cat enjoys, stick with that brand because cats may rebel if they don’t like another brand you may pour in their litter box.
If you thought cats are picky about their litter box, be thankful cats aren’t designing your home and picking your furniture as well.