Even as a new owner, you must abide by the current rental situation. If tenant is month to month, you must check with current owner whether 30 or 60 day notice is agreed upon (if it's more than 30 days, it should be in writing) and then you can give notice of anything you want to change by whatever terms had been agreed upon. If it is a long-term lease, tenant is protected until expiration (but I've heard of buyers and sellers paying the tenant to vacate early). Joyce Muecke, RE/MAX Realty 100, Milwaukee, WI
Here is also a link to the landlord tenant laws: http://datcp.wi.gov/consumer/wisconsin_way/
Good luck to you.