What rights do people who live in a rental house have when the unit is being sold?

Hello, I currently rent a house in Los Angeles with my family. We have lived here for close to 15 years. My aunt owns a duplex and we have paid rent during the entire time period. Recently she informed us that they will put both properties for sale. Its kind of a short notice and everything seems to be turned upside down on us. Strangers have been walking in our house to see it and it feels weird. I took a look at the listing for the houses and it says that the units will be turned in vacant. So I am like WTF?! So I was wondering what rights do we have if any? I mean we are scrabbling trying to find a new place to live now. Any responses would greatly pretty appreciated. Thanks.