6. This section shall apply to all rental residential premises except
owner-occupied dwellings with less than four units. However, its
provisions shall not be given effect in any case in which it is
established that the condition from which the complaint or action arose
was caused by the tenant, a member of the tenant's household, or a guest
of the tenant. Nor shall it apply in a case where a tenancy was
terminated pursuant to the terms of a lease as a result of a bona fide
transfer of ownership.