When you apply for your licence, you have to say how many dogs you want it for. I got what I asked for. It's determined by how much space you have really.
I do walks straight from my house - I never drive dogs anywhere. We have nice walks nearby, so that's easy. I also don't pick dogs up or drop them home, that is up to the owners.
I don't get any dogs through agencies. I simply did leaflet drops and on line adverts (Facebook/Gumtree) at the start, and within my first year I earned £33k, and then it grew a bit each year after that. Remember, I have no overheads, no staff to pay, no commuting costs, no parking fees....so that counts as well, if you are currently spending on those things.
Within a few years I was able to stop taking any new dogs, and just keep a nice turn over with the dogs I knew. Which is good, as there are no nasty surprises.
If you have any other questions, please do PM me, in case I don't see this thread.
I think it was easy for me to give this a bash, because I had to take VR. I can see it would be much harder to hand in your notice and try it, because of fear of the unknown. I didn't have much to lose, as my VR package was 2 years salary. There is NO way I would go back to work in an office now!!