An in-home cat-sitter is someone who will go to the home and care for the cat or cats while their owner travels. Feeding, watering, litter-box care and play-time with the cat are the obvious duties of a cat-sitter.
Some kitties do not like cat-food from the fridge so I am often microwaving the food to the proper temperature. Some have vitamins sneakily tucked into the soft food. Some are a little pudgy and need to be exercised by rolling a ball 125 times down the hall. *whew* If the cat is lonely after a few days I have stayed longer, sat and read for awhile, letting the cat have a snooze on my lap. Brushing the cat helps to bond with it and will keep hairballs down while the cat waits for the owner to return.
A cat-sitter works 7 days a week. Most people travel and the holiday times such as Christmas, Easter, Thanksgiving & March Break will be the busiest. That being said, the cat-sitter must take holidays at the off-times if your clients need you. You must be willing to go to your client's homes during all weather. A snow-storm or blizzard can't stop you from getting to the cat to feed and water it. I have seen myself out on the road during icy, snowy weather when most people stay home. I just take my time but I get there.
There will be other duties to provide such as bringing in the mail, changing lights and opening and closing curtains. Plants may need a watering and a check on thermostats and air-conditioning units are sometimes necessary. I have also fed their fish, outside birds and believe it or not, feral cats. Yes, a lot of cat-owners also worry and care for the ones that wander onto their property.
So, that's just a bit about becoming an in-home cat-sitter. If you are considering it, I think it is the best job in the world. I can't think of anything I would rather do. You have to love cats unconditionally. I do and always have. You will have to decide if you want to work for a pet-sitting company or start your own service. That's your first step.