If one borrower has a lower credit score and/or larger debts that could affect loan qualification, the lender may raise the interest rate or deny financing. Also, if one co-borrower is not able to contribute financially to the housing costs, including mortgage payment, the other co-borrower will have to cover the shortfall. It can be challenging, as well, to get both parties to agree on who is responsible for what and what to do if one party wants to sell the home but the other does not.