Tenant Question: "Room-Mate", no lease, now estate owned home

[Zach Schwarzmiller]

My friend's mother has just died and her boyfriend had been living in the house renting a room (for quite some time now). The house is now owned by the estate and my friend is wanting to list and sell the house come April 1, 2015 and wants the boyfriend (room-mate) out of the house by March 31, 2015. I am helping him draft a 20 day Notice to Terminate Tenancy (way earlier than 20 days); however, the question is should we put him on a short-term lease as well? He doesn't expect there to be any issues, but just in the case he hasn't moved out he doesn't want it to stall the listing, showing and sale of the house so he's just trying to protect himself in the meantime. Anyone have any suggestions on a good way to proceed? Home is located in Edmonds, WA (Snohomish County). Thank You,