Buying an owner occupied duplex with tenants in Washington?

[Kirsten Crotts]

I just bought a duplex in Puyallup that I will be moving into. Both tenants are month to month and one side hasn't paid rent in two months (this is the unit I plan to vacate and occupy). The property is closing this Monday the 20th, how do I go about vacating the non paying tenants so I can move in? Do I need to give them 20 or 30 days notice in Washington? Can I send the letter to vacate the day of closing or do I have to wait to give notice to January 1st? Thank you.