You will find in order to clean commercial kitchens, that you need to be qualified to a certain standard, ie. Hygiene Certs etc. You also need to ensure that your liability insurance will actually allow you to cover this sort of work. All H & S paperwork etc also needs to be top notch, as getting the cleaning wrong could potentially cause harm to your client's customers etc. The client could also expect you to be responsible for extractors, ducts etc, which would of course mean a large up front expense on your part to purchase the correct equipment.
Regards,
Rob