What are my rights as a buyer if a tenant is occupying a power of sale property in Ontario?

If a legitimate tenant is occupying a power of sale property, you generally acquire the property subject to that existing tenancy, and you step into the role of landlord once you close, rather than gaining any special right to remove the tenant simply because of how the property was sold. Ontario's tenancy protections are not suspended because the previous owner defaulted on their mortgage, and the change in ownership does not by itself give you grounds to end the tenancy.

Your rights and obligations going forward are the same as any other new landlord's: you can end a tenancy only for one of the recognized reasons and through the proper process, and in the meantime you are responsible for honouring the existing lease terms, respecting the tenant's rights, and maintaining the property. This is worth factoring into your purchase decision, since an occupied property with rent well below market, or a tenant with strong legal protections, changes the practical value of what you are buying compared with an empty one.

Try to learn the tenancy details - rent, term, and any deposit - before you commit, and speak with a lawyer about your obligations as the incoming landlord.