Notification requirements regarding non renewal of lease

[Rob Myers]

I picked up a duplex a couple months ago and inherited two sets of tenants that can't seem to get along.  The relationship is turning into a Jerry Springer show with some very immature behavior.  I may be choosing to not renew one or both of the leases this fall and electing to start over with tenants that I can screen.  I read the lease and couldn't find anything specific regarding my notification responsibility.  I checked the WI statutes quickly and couldn't find anything either.  I want to give proper notification but don't want to leave any more time than I need to in case someone gets spiteful and decides to trash the unit before their lease is up.  Is anyone familiar with the requirement in Wisconsin or more specifically Milwaukee County?

Thanks