Tenant Not Under Lease

[Corbin H.]

I'm preparing to sell a property in Washington state and the tenant is being super uncooperative. My real estate agent asked for a copy of the lease to see what the tenant agreed to. I requested a copy from my property manager. The property manager said the tenant is on a month to month so a lease was never signed. 

What does this mean for me:

1. Damages done to the property?

2. What rules have to be followed for showing the house?

Any insight or advice would be greatly appreciated.