The Times article quotes someone saying he knows people with six figure incomes from dog-walking businesses. I don’t. And I bet you don’t, either.What is interesting about this quote is that I see a six figure income as a dog walker as plausible if you are talking revenues. Dog walker is actually a tough gig if you are going to make it a profession and give high end experience. You need a vehicle to transport the animals to a dog park. You need insurance (liability and personal health). You need to be bonded as you likely have access to people's houses when they are at work. You are dealing with beloved animals who may well decide not to listen at a key time.
So it takes trust and there is a lot of effort involved in building that reputation. The effect of reputation (do you trust the professional or the new person) is an effective barrier to entry to new dog-walkers who simply can't just compete on price. So this creates a space for some dog-walkers to end up able to generate a lot of revenue.
But this sort of heavily networked profession is more than just picking up dog poop. It's also about controlling lots of animals, knowing how to run a high liability business and developing an impeccable reputation -- being able to sell yourself as trustworthy. Ending up in that sort of profession where you are the real product being sold (musicians, car salesman, model) has always been a alternate path to a decent income. But there is a huge element of risk in all of these approaches and not everyone can end up with a highly successful network.