You will need a cat carrier. At the very least you will need it to convey your cat to the vets every once in a while. There are generally speaking two types of carrier that are readily available today. They are the two part plastic carrier and the more traditional cane carrier, both types should have a blanket or similar placed on the bottom and the carrier should be big enough to allow the cat to turn around when fully grown. If you need to move several cats at the same time you will need one carrier per cat.