When using pictures that contain clearly recognizable places or other property (such as pets), a property release protects you against legal claims by the owner of the property.
In general, property releases are obtained when using pictures of property for commercial purposes, such as in ads or brochures. Editorial use (news photos, for example) do not usually require property releases although in some cases it is common courtesy to obtain permission.
When obtaining photos from third-parties, ascertain that the image is accompanied by a property release. Most reputable stock photography sources have model releases and property releases for their images.