A good tip would be to advertise in a local dog show catalogue, as show people often need dog sitters when they are away at shows all day. They also recommend people to each other once you get going. I did this back in the late eighties, before it became well known, and I really enjoyed the freedom. I specialised in kennel sitting, so owners could get away and it meant I could take mine with me. Cliverton are a good specialist insurance company. Why not also train as a microchipper, Pet Detect do courses in different areas, and if the government bring it in as compulsory there will be lots of work. Animal first aid is also a good thing to have, and you could ask you vet to give you some training in giving injections in case any animals need them.