If both you and your guarantor become unable to make the repayments, the lender would likely try and find a solution to help you manage the debt. This could be extending the mortgage term to reduce the monthly repayments, or allowing the deal to be switch to interest-only for a period of time while one (or both) of you gets back on your feet. However, as a last resort, the lender will seek repayment for the debt from the guarantor's savings/property. Your property may need to be sold to cover the debt. If the guarantor has the means to repay the loan but is not willing to, then that is a breach of their contract with the lender and legal proceedings may therefore take place.