Eh...it was a rental. MJ didn't have any money. He blew it all on his crazy/lavish lifestyle...that's why he was doing that comeback tour. The house was rented for him by the tour promoter.
The ironic thing for Dr. Murray...I don't think he ever even got paid by MJ, so he killed MJ by malpractice, and ruined his own life...for no money at all.