The tenants can call the city and complain (city may then do an inspection). It is recommended for the landlord to give the tenant some kind of compensation and sign a N11 form to end the tenancy. When the unit is vacant the landlord can obtain the proper permits to ensure it is legal before renting again in the future.
If you believe an illegal act is being committed at your rental unit, you can request to get a copy of the police reports as per the Freedom of Information Act. However, it is not a quick process, and can take some time.
It depends. Have to make sure the entire rental unit isn’t being used for the business. Ask the landlord how they are affected by this? See if the area is zones, are they allowed to have a business in that area? Landlord is usually involved when the insurance company doesn’t cover the commercial use or if the municipality fines the landlord
No, the landlord does not have to install an AC unit since it is not classified as a vital service unlike heating (which has to be at 20 degrees). The landlord should specify in their rental agreement that if the tenant wants to install a AC unit they still need permission from the landlord and it will be at the tenant’s expense.