Provided you understand the private property laws in the United States, then you can pretty much safely assume that Wisconsin is for sale, or at least portions of it. The state as a whole? Well, since there isn't one owner of the land, that's not even plausible. Buying power? Based on history, that's entirely possible.
I think that Wisconsin might be for sale, but so is every other city and state in this country. Everyone wants what they want, and we can be sold to the highest bidder. People are too concerned about their own interests when we should be thinking about what is good for society as a whole.
I don't understand how a state can be for sale. Even if a legitimate business invests in the state and receives benefits for doing so, the state is not for sale and the business cannot buy it as an investment. I do think that to prevent such issues from rising up, governments at all level need to be transparent so that they are not accused of selling their states.
No, Wisconsin is not for sale because it is a part of the United States of America. The government will not let one of its states be bought by a wealthy person. It would be unlike the US to allow any of its territories to be up for sale; Wisconsin will not be the first.