Hello OP - I'm a dog walker and started up in February after 10+ years in retail :)
Dog walking is a very unregulated industry. You don't need any qualifications, experience or even insurance to set up business (not that I advise doing that - I'm just setting the scene). However, it's not an easy way to make money and I'd advise being aware of the pitfalls as well as the benefits before you decide to go for it.
I would say that anyone setting up needs to have some basic qualifications in dog behaviour, training and first aid. Personally, I'm fully insured, and I have canine first aid and dog behaviour qualifications, too. My next step will be to do some dog training classes, but with COVID this has all been put on hold temporarily.
In some ways it's the best job in the world, but it's not always easy and you have a lot of responsibilities and decisions to make every day to keep yourself and your dogs safe. Some things to think about are:
1 - whether you're truly happy to walk in all weathers, including 50mph winds, rains and storms. It can be utterly grim out there in the winter months - especially if you have 5-6 hours of walks booked in!
2 - are you going to do group or solo walks? Groups are where the money is, but they're a lot more work than solos - you have to look at whether the dogs will get along, whether they'll go off-lead, whether they can walk nicely on a lead (and if not, can you teach them) and how you'll transport them all safely.
3 - what you'll do if a dog becomes sick or injured? I've only been open for ten months, but I've had a dog cut their paw whilst out with me, plus another who was physically sick too. Do you have enough knowledge to treat them or would you need to get them to a vet? If they need a vet, what will you do with all the other dogs in your care?
4 - what will you do if a dog in your care bolts, gets into a fight, injures another dog or, heaven forbid, bites another person? As the walker, you are liable if the dog is out of control, and any dog can spook or get frightened. Knowledge of body language and behaviour is very helpful here!
5 - be prepared for busy and quiet times. It's not a career that brings in consistent money. Some weeks I'm slammed and bring in nearly £500, and others I'll earn £20 a day, if that. Do your outgoings and lifestyle support those kind of fluctuations in income?
6 - what will you do if you're sick or injured and can't walk the dogs? Is there another walker who can help you out, for example, or maybe a family member? My husband is covered on my insurance and has filled in for me a couple of times (with clients consent, of course).
7 - make sure you have contracts in place with your clients. You need to know everything about your dogs, from their diet, to allergies, to behaviours - likes and dislikes, how they walk on the lead, are they on medication, can they go offlead (always get the owners written consent for this), what vet they're registered with etc etc.
Feel free to PM me if you want to talk off the boards, and best of luck with whatever you decide! :)