Your rights and obligations are unenforceable absent a contract. A contract may be inferred from your past acts. if there is a contract, then you have tenant rights. If there is no contract, you may be considered a trespassor with no rights. If you are a tenant, you owe your landlady rent. If you are a trespassor, you can be criminally charged.
Clearly someone has money issues. You didn't say if sistr or your friend own the house. You should have either the person who owns the house, or the person who holds the lease on the house, give you a written document stating the deal between you. Right now it appears that you have a month to month lease verbal lease, which requires that you receive 30 days notice to evict you. If you get the contract in writing, with a end date, then you have a better lease.
By the way, if the sister or your friend own the house, then a written lease for a term (say end of the year) would have to be honored by the loan company foreclosing the house. In any event, if you have a written lease, the loan company could not evict you for 90 days. (New federal laws now in effect).
If the sister or your friend do not own the house, but have a written lease and the landlord isnot paying the rent, then they MUST continue to pay the rent to the landlord until they receive an order to pay someone else. They would then be entitled to stay the longer of either the end date of their lease, or 90 days, if a loan company foreclosed the house.
You should consult an attorney to review your documents. The sister and your friend may want to join you.
Good luck. jim
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There is a federal law passed in May 2009 - "Protecting Tenants at Foreclosure Act of 2009" that gives tenants the right to stay for the term of the lease as long as the lease is at arms length. On a month to month lease, the tenant is entitled to at least 90 days notice. Obviously you need to stay current on rent. If you sign a written lease then in event of foreclosure, the lender has to recognize the terms of the lease