If two people co-own a property as 'joint tenants' then, when one of them dies, the property does not form part of the deceased person's estate (as therefore can't have any of their debts charged to it). The ownership of the property simply passes to the survivor.
If two people co-own a property as 'tenants in common' then, when one of them dies, the property forms part of the deceased person's estate and therefore can have his/her debts charged to it. (That applies even when, through the deceased person leaving leaving a will or through the laws on intestacy, their part of the house was due to pass to their partner).