Landlord needs a place to live, wants to move in

[Joseph Smith]

My partner and I have been renting a manufactured home from a friend of a friend since August 2019. Our lease goes until August 2020, but we are going to be leaving sometime in the beginning of June for new jobs. The security deposit was only $300 and we've been expecting to lose that. 

The landlord was renting to us because he was living with his girlfriend, who is now his ex girlfriend and who wants him out of her house. She has said he has to be gone by April 23rd-we usually pay $850 rent on the 22nd each month. Landlord has no other place to stay because of Covid-19, none of us want to live together but we're amenable to the idea because a decrease in rent would be nice and it's only for a month. 

However, I'm wary of the idea and want all the right documents in place before this happens. Our lease is very standard and we live in WA state if that matters. The home is located in a park that charges the landlord a lot fee of around $500. The home has 3 bedrooms and two bathrooms and a full kitchen. 

We have the right to deny him moving in, based on what our lease says, but if we decide to all bunk up what kind of documents should we prepare to ensure we're protected?