Even if it’s a mundane task like walking dogs, you could start the next (or only) full-service dog walking and grooming service in your town (where dog owners rave over your business and always refer you to others). You can also hire other dog walkers as you grow, and turn your side hustle into a sustainable enterprise. You just have to do the work, and do it well.
Great list. I have another to add that’s almost as easy to do as going for a walk! Provide a litter cleanup service outside commercial properties for property management companies. The work is done on foot using simple hand tools. I started this service in 1981 as a side hustle and quickly grew it into a lucrative full-time business that I still operate. I share my experience with others in my book, Cleanlots, as well as offer free support.