The experiences I have had pet setting have all been for family or family friends. It has been mostly small dogs such as dachshunds and yorkshire terriers. I do have experience sitting medium sized dogs as well, but the ones I have sat are mixed breeds. I have only sat one rabbit.
When pet sitting, I have walked, fed, watered, and played with the animals. Between walks and meals and play times I normally do a bit of cleaning around the house. I clean bathrooms, bedrooms, living rooms, dining rooms, and kitchens.
I have never been paid to pet sit specifically because normally the animals have just been a part of the overall job. While I watched an 11-year-old boy for an entire summer, I lived at the house and took care of the house and the dog as well.