There appears to be some considerable work needed, just in updating the decorating, removing wallpaper and repainting. That does not even take into consideration all the unfinished projects on the house. I would strongly recommend that you use a Buyer's Agent to protect your interests (it won't cost you any extra and may even save you money and headaches), as well as a certified home inspector's thorough examination of all aspects of the property.
Taking both of these courses of action will definitely be in your best interests, as the property is being sold in an "AS-IS" condition without any guarantees. Your Buyer's Agent cana also set you up with a Home Buyer's Warranty, so that any service call would only cost you a maximum of about $60.00, even if a furnace had to be replaced.
Buyer's Agent's commissions are paid by the Sellers in Wisconsin. It would be wise to have someone familiar with the area and local codes to represent you in the process to minimize your risk.