Potentially, dog walking is an excellent idea! I've seen women (not so many men) walking 6 dogs at a time! I don't know how much to charge, I don't know much about dogs either, but you can look in the phone book to see who else is doing it, and a phone call will give you their rates and services. Part of the trick is setting yourself up with dogs that get along with each other, similar size, I guess, to make things easier for you. You can make tax free cash money walking dogs, and you can advertise in public laundromats, supermarkets, and any place with a public bulletin board. I've made money advertising this way, I'll go to someone's home and give manicures in the evening, sometimes an afternoon on the weekend. Many women come home from work and would like to have their nails done without the wait at a nail salon. Over time, a steady clientele is developed.
During the summer, people need dog walkers, pet sitters, and even plant waterers for when they go away on vacation. Not everyone has a reliable friend or relative to care for their pets or plants. I once asked my brother to water my plants for a few days, and he flooded every one of them...there was water all over the floor! ADVERTISE! As long as you're neat and clean in appearance, pleasant and reliable, you can really help a lot of people and make some money in the process! You can run off flyers on your computer to start, and you can advertise for free. You can also try advertising on Craig's List.
If nothing else, you can advertise online just to get an idea of the potential market without investing any money.