Contract for Deed- Owner filing bankruptcy

My mother and sister purchased two contract for deed  houses from a couple, who were family friends, around 2 years ago- here in the state of North Dakota.  The houses are owned free and clear by the couple,  They have since separated and the husband has moved to California.  He is now planning to file bankruptcy.  We are unsure as to where that places the contracts.  My mother's income is very little and with that and her age, she will not qualify for a mortage to continue purchasing the house.  In addition, my sister's credit is such that a traditional mortgage is not possible.  I am struggling to find bankruptcy exceptions or any information on where this places the contracts. Will they have no option but to apply for a mortgage?

Any tips would be tremendously appreciated.