What are my rights as a someone who isn’t on a lease and the owner of the house recently passed away?

First, I'm sorry for your loss.  I know it must be hard trying to grieve your loved one and then have to deal with this.   The short answer is that if you are not an owner of a home, or are not on a lease, you have no legal right to occupy the home after the death.  Although you had permission to live there from the owner, he is now passed and that permission has expired.     The long answer is that you did have permission to occupy the premises.  If you refuse to move, the owner of the house must file an eviction action to force you to move.  This would be the only legal way for the owner to force you out.  Yes, the new owner of the house should give you 30 days notice to move.  But the question is, who is the legal owner now?  Has a probate action been filed?  Once a probate action has been filed, the Personal Representative can provide you with that notice and request that you move in 30 days or you may be subject to an eviction action.  The hard part is that you don't know how long it will take for the ownership of the house to be determined.  My suggestion would be to start looking for another place to live now.  If you find one, let the sister know that you will be moved out within 30 days.  An alternative would be to let her know that you plan to find another place and ask her to agree in writing that you will move out within 60 days.  That may buy you more time, however, I feel whichever avenue you decide to take, the end result will be the same, that being you have no legal right to live there and must vacate the premises.