Reading between the lines, you rented a property and you are subletting to your SSI receviing mother in law? Hopefully, everything was properly represented to the SSA so there is no fraud there.
I presume you stopped paying the previous landlord upon the foreclosure. You should retain the money to make those payments until you find out who to properly remit them to.
Your lease was extinguished by the foreclosure. Washington state law allows the new owner to either kick you out with 60 days notice or renegotiate a new lease.
The person who now owns the property in such cases is almost always the foreclosing bank.