Strong odds for being a hoax.
Just on its face, the handwriting seems to be female. They wrote that they have put their house up for sale. If this is the case, it should be *easy* to determine who sent it, if it is not a hoax.
Here is a picture of the grandmother.
http://i.imgur.com/yJIcAcK.jpg
On the basis of that picture I call hoax.
