It is important to determine who the tenants are.
Ask the landlord for copies of all lease documents or tenancy agreements. If they are not available from the landlord, ask the tenants for a copy.
Often lease agreements have been registered in the land title registry and copies can be obtained. Obtain the correct legal name and updated contact information from all tenants.
Determine how long they have been a tenant and the nature of their business. This may be required to determine if their business complies with the uses of the building, or if they are they violating any provisions of the lease agreement. It is also useful to determine if the tenant is related to the landlord.