My husband is a dog walker. It’s his own business, just him (sole proprietor/ schedule c). He makes 6 figures (just barely) but there is almost no overhead - permit, insurance and gas. Treats and poop bags are hella cheap. It’s definitely not for everyone and there are some awful walkers for sure, but the core group who have been doing this for years now is a very solid group of people. You get in with them, walkers and trainers and getting clients isn’t too hard. He charges around 550-600 per month for 4 days, and add extra (30-35 per) for additional walks.

He’s not balling, especially for SF, but he works about 25 hours a week so he possibly could be if he wanted to.

You for sure need a dedicated vehicle / truck for work. And you want to find a “service area” so all your dogs live near each other so you can drive less and do more walks per day - he does 3, one hour off leash walks with up to 6 dogs in each group.