Back here in Washington, we don’t pay sales tax when we pay the neighbor to come over and walk/play with Sonny while we’re away for a day (or we wouldn’t, if we ever get around to asking the neighbor to do it). Those services are exempt in Washington. Dog walking services are also exempt in Texas and Wisconsin.
It’s less clear if tax applies to a neighbor’s dog walking services in Minnesota. If you pay a neighbor to drop by and play with/feed your dog in your absence, tax probably doesn't apply. However, if the neighbor has established a business of providing these services, or advertises these services for sale, sales tax likely would apply. Extra charges (for walking, picking up poop, etc.) are also taxable. Presumably this is true no matter how old the neighbor, or how advertising occurs.
In New York, “pet sitting services rendered by an individual who is hired directly by a private home owner or lessee, and who does not offer these services to the public as part of a regular trade or business, are not subject to sales tax.” However, sales tax does apply to pet sitting/dog walking services provided by a person in the business of pet sitting or dog walking. This is because “pets are considered to be tangible personal property … [and] the maintaining and servicing of pets is taxable.”
That said, New York doesn't tax any goods or services needed to acquire, sustain, or maintain a guide dog, hearing dog, or service dog.