I am not an attorney. I have no idea if the law unilaterally requires you to notify tenants or not. However, I assume selling the property has a potential of attracting a buyer who intends on owner occupying the property. This means you have to follow the law regarding evicting the tenants. So, if you want to have the flexibility of accepting the highest bid, which may come from someone who plans to owner occupy, I would disclose the sale to the tenants. Beyond that, I'm sure one of the apt attorney's here will provide you with more specific legal info.