In 2017, there were almost 90 million pet dogs in the US. Which has opened up a huge opportunity to make money online as a dog watcher or sitter. Specialized sites like Rover or Care.com connect pet owners with pet walkers, sitters, and boarding houses to help look after their best friends when they’re at work or on a trip. If you’re an animal lover, you can make extra money and get to spend some quality time with a furry friend.