Legal Question in Wills and Trusts in California

It depends on whether it is an existing encumbrance, created prior to creation of the life estate, or an encumbrance created by the life tenant during the life estate.

If the life tenant creates the enbumbrance after creation of the life estate, the life tenant is obligated to pay the obligation secured by the mortgage or deed of trust. (Pryor v. Winter (1905) 147 Cal. 554, 559.) If the lender foreclosed, they would only take a life estate interest, and it would not terminate the remainderman's insterest.

If the encumbrance was created prior to the life estate, however, then the lender can foreclose and would take the estate as it existed prior to the life estate, which would be the entire fee simple. In those cases, both the remainderman and the life tenant are responsible for the obligation secured by the mortgage or deed of trust, because a foreclosure would terminate both their interests.

It depends on the document, and ultimately what a court says, but you should try to work out a written agreement with your husband's stepfather regarding the division of expenses. He certainly is responsible for a lot of the current maintenance expenses, and likely at least a good portion of the mortgage, and if he can't pay those, the life estate would revert to your husband.