Best Way To Handle This Lease Violation

[Lawrence Rutkowski]

Hello BP friends. I have a dilemma regarding the best way to move forward regarding some serious lease violations by my tenants.

I own a duplex in Buffalo NY, however I live in TX now.  

I have tenants that have been in the lower unit for the past 3 years, upstairs people are moving out after 2 and my step mother is showing the place.  Come to find out the downstairs people took it upon themselves to take over the entire common area backyard  by erecting a full size (inflatable) above ground pool and a slipshod deck attached to it, hot tub, horse shoe pits and a fire pit. They also set up a full size refrigerator right on the back patio. (looks extremely trashy)

They never asked.

This is my fault as I've been hands off, but the chickens have come home to roost.  

So:

I have not contacted them as I just found this out 30 mins ago.

Their lease is up in October, and as of right now I do believe they intend to stay.  This may change after our conversation about how they will have 10 days to fix these violations and the damage they've caused to the back lawn.

Do you think it's best to address this immediately and run the risk of having them skip rent for September? (I do have October's and their security deposit), or should I wait to receive and cash the check?

I myself am leaning towards immediately (officially tomorrow morning), but what do you all think, and what do you think the best course of action is?  Thanks.