If the landlord buys out the tenant then that typically means the unit is rent-controlled, which means the tenant does not have to leave, and their rent doesn't change, just because the building is sold (rent control goes with the building, not the owner). Just adding in case that's not clear to other readers here. Tenants can and do accept buyouts, but just pointing out that a tenant's rights under rent control do not end with the transfer of the property to a new owner.