When the home is sold the second trust (mortgage) deed as well as the first will be paid off in full as part of the transaction. As such, there will not longer be a second trust deed (mortgage) left on the home for the property's new owner.If you want the "ex" to be responsible for the $18,000 second mortgage, you need to carefully read the presumed marital dissolution agreement that you have in that the agreement and judgment should determine if the "ex" is responsible on it or not.