I did this all throughout middle school. It’s a great way to get exercise, money, and time with dogs! A lot of older people or busy people will pay you to walk or run their dogs because they know the dogs need it. I walked a dog 3 times a week for 30 minutes each day for $5 a walk. Make sure you bring a plastic bag though because it is very rude and gross to not pick up after the dog. See if your parents know anyone or ask some neighbors if they need a dog walker. If you live in a neighborhood with a pool then you might be able to put a flyer there to advertise.