[Studio25]

I wouldn't worry too much about the insurance thing. You can put together a contract which absolves you of financial responsibility for their dog's behaviour, and other eventualities such as the dog escaping its lead and going missing.

You can't mandate against negligence, so if (for example) a fine is charged for the dog fouling the pavement and you don't clear it up, that would be your responsibility.

You can pick and choose your customers. Not many owners are stupid, but as with everyone it's the stupid minority that make life difficult for the rest. Anyone who gives you a detailed report of their dog's usual behaviour and likes/dislikes will probably be OK. Anyone who just hands over their dog and expects you to work it out for yourself should be approached with more caution. Anyone who gets upset that their water-loving Labrador (or whatever) comes back wet is obviously an idiot and should be avoided.

A short questionnaire about the dog's personality can be worded so it helps assess the owner's personality too.

A dog owner would probably only expect to pay the national minimum wage to start with - £3.68 per hour for someone your age. When you get a few regulars you will probably find they will pay more just to get someone they can trust and/or someone who is willing to book times that are convenient for them. There are two dogs in this house, I'd expect to have to pay more for walking them together, but not twice the rate for just walking one.