Depending on what he wants to do, you can either (1)remain as tenant and make the monthly payment on his behalf.(2) Ask him to sell to you for an agreed price , which requires you qualify on your own or with other persons(3) Sell the home and go your separate ways (4) Abandoned ship ( Not recommended).
The liability remains mostly with him ( Mortgage,Credit ,Taxes,Etc).
Since you are most likely not upside down on your home, you have many choices. Please figure the cost to sale at around 7-8%.
Call or write anytime.....