Landlord Selling Building

Hi There, My landlord is selling the building which includes 3 apartments. Do I have to give the real estate agent access to my apartment for viewings for potential buyers? I just re-signed a lease for another year. If he ends up selling the building the new owner needs to honor my lease correct? I'm also renting out one of the bedrooms in my apartment to my sister. Does the new landlord have the right to make us both sign the lease even If I've been the only person on the lease for the past 3 years and don't want anyone else on it? Thanks for any advice you can offer.