The building code classifies a doggie day care as a "B occupancy", which is the same as an office use. Most spaces that have been legal offices or stores (M occupancies) should be good candidates for conversion to doggie day care, whereas industrial buildings (F occupancies) or warehouses (S occupancies) may be difficult.
The building code sorts the ways that buildings are used into separate "occupancy classifications". Every building is given an occupancy classification when it is built, and each occupancy classification has different building code requirements that go along with it. The requirements for a building to be used as a B occupancy doggie day care are stricter than the building code requirements for a warehouse or industrial building. A "change of occupancy" is when there is a change in the building's use that would place it in a different occupancy classification.
This could mean adding more exits, emergency lighting, or other safety improvements to a building that is currently grandfathered as either an industrial or warehouse use.