If the property was listed for sale prior to SM going missing, it is possible that it was a preliminary step towards a parting of ways. I still feel that when he said "Oh, Suzanne," it conveyed that she had done something that pushed him over the edge. Moo.Yup, this is why I think the rental property was listed for sale by the Morphews long before SM became missing.
Question is if BM wanted the proceeds all to himself and also investigated on how to get that done. Via guardianship. Then we are talking premeditated murder.
IMO