Not long ago, Calgary experienced its worst mass murder ever when a student pulled out a knife at an end-of-school house party and killed five people. Recently, that house went up for sale.
In Ontario, as in most of North America, there is no legal requirement for a seller to disclose things like murders or suicides in houses. There is, however, a small but growing body of case law that says that, if there is a stigma, the seller should disclose in order to avoid emotional trauma to the buyer. If you don’t, and the buyer finds out later (which they will – they neighbours will always talk), you could face a lawsuit.
Ontario is technically a buyer-beware system, but often, disclosure is the best policy.