According to new ruling of Aagha e sistani if someone owed money, Khums is not wajib if saving is lesser than bebt but this is if this mortgage is with the niyat of loan.
But if one has borrowed money from bank with the niyat of istenqadh means not with the intention of loan. The knowledge that the bank will sooner or later force him to pay the capital as well as the interest does not affect [the lawfulness of] his taking the money.In this case khums is wajib.
Whatever saving at home or bank or anywhere khums is wajib
Related to Gold if it was used then Khums is not applied.