I use a dog sitter/walker, she's great, and will even come short notice (like when I had to dash over to Chester with Leah, she came and sat with the others as hubby was at work)
she has a few clients in the village where I live, as well as nearby, and although I work shifts and only tend to need her when both me and hubby at work a same time, she still manages to fit me in, I assume her other clients are more flexible.....she doesn't need to take mine on the street, they are quite heppy to wander round the garden with her, it's more the company, I ask her to stay for at least an hour, have a cuppa, put the telly on, and let the dogs chill out for a bit - they behave very well for her too, and she always brings a treat

I don't know how much she earns in total, but like you say, it's flexible, and as long as you can get out to your clients you should be fine
....the most perfect creature of Heaven....