Should I have a lease

[Christopher Howard]

Hello all. I need some advice. I recently bought a 2 family and am living in the first floor while fixing it up. The upstairs unit is currently occupied by a contractor/friend of mine who has agreed to fix the place up on his own (me paying for materials) if he could have a break in the rent (charging a couple hundred under market). He is an old timer contractor that we all know and love and is therefor not a fan of an actual written lease. I'm wondering what people recommend here. He is registered (to vote) with the town so it's not a secret that he lives here. I'm wondering if I should let him live without the lease as he's increasing the value of the property while still paying rent. Also how should I process the payments so that I can still write off the property as a rental? He pays cash.