Last year, a couple in Chatham bought a piece of vacant land, intending to build a home on it. They received a building permit, and began to excavate. Partway through, they discovered several bodies.
It turns out that the land was once owned by a church, and that had been the graveyard. When the church moved in 1861, all of the bodies were supposed to have been moved to a local cemetery. Unfortunately, they missed some. Even more unfortunately, under Ontario law, the homeowners are technically responsible for the cost of an archeological assessment to determine if there are other bodies, and the cost of moving the bodies to the new cemetery.
If you are at all concerned, you can go here and find out whether the land you are buying was once a cemetery.