A sale does not by itself end the lease
Under Wis. Stat. § 704.09(3), lease provisions that are not personal to the original parties can be enforced by or against their successors in interest. The change in ownership alone does not cancel the tenant's existing lease rights. Check the lease and amendments, and make the occupancy part of the written sale terms.
Notice and possession are separate from selling
If you want the house vacant, ending a tenancy is a separate step; the sale itself is not a notice to leave. Under Wis. Stat. § 704.19(3)–(4), notice to end a periodic tenancy must be in writing and generally at least 28 days, with statutory exceptions. It must identify the intent to end the tenancy and the termination date. The lease and type of tenancy affect the required notice and possession process. You can also ask us about selling with the tenant still there rather than seeking vacancy first.
Account for the security deposit
Keep the deposit amount, records, and any existing accounting in the sale discussion and written closing terms. Under Wis. Stat. § 704.28(1), (4), the landlord may make only permitted, reasonably necessary deductions, and the remaining deposit is generally due within 21 days after a specified tenancy-ending and move-out event. That return clock follows the event listed in the statute—not the property's sale date by itself.