smelly tenants in multiplex

[Lane Smith]

I am purchasing a multiplex and before the initial walk through I was told to be prepared for a dirty tenant. It was not too bad (dirty carpet and sticky floors) but the smell of trash and body odor was fairly repulsive. I could smell the apartment interior when I was in the front porch and in the basement. Is this an actionable condition? I do not want to remove them since they are long term tenants but I do not want to drive away other tenants because they have the apartment smelling like an outhouse. They are currently month-to-month (1 year contract was up 6 years ago) so I could get them to sign a new lease with more restrictive cleanliness clauses but I wanted some input before I proceed. Thanks