Appraisal data

Does your county appraisal data somehow indicate that the building is a rental property?

No.  This usually comes from either electrical or water connection data.

Generally speaking there may be a variety of different data sources that can be used to find out information about the building type. For instance, you can google "real property data" with the name of your county or jurisdiction. Other data tools related to housing are described here:  https://nchh.org/tools-and-data/data/