tickets, how do you turn one mortgage into layers of various credit ratings? How can a $400K mortgage be broken into a $100K AAA MBS, a $100K AA MBS, a $100K C MBS and a $100K D rated MBS? These are just numbers I’m making up. Who buys the C and D tranches? Who insures them, who pays for the insurance, and who will be left holding the back when the mortgage isn’t paid? If the owner is upside down, who pays off the MBS? I suppose the upper levels get paid off first.