Most dog walking apps let you create a profile for free, but they take a chunk out of your earnings. How much you pay depends on the app you use, but it can range from 20 to 40 percent.  Some apps charge a flat fee after you reach an earnings threshold.  Because of this variation in pricing structures, it’s important to do your research, read reviews and understand how much you’ll take home at the end of the day if you decide to become a dog walker.