Notify Tenants of Sale?

[Amy E.]

What is the etiquette for notifying tenants of the sale of a property?  For reference, these are single family rentals, some rented Section 8 and some not.  Some tenants in a regular lease and some month-to-month.  

Do I wait until after the due diligence period, after closing, etc.?  I have no idea what the new owners intend to do with all the properties.  It is an investment company and when I googled them they have rentals but they also do rehab flips.  Not sure what their intent is for these.