You should check the possibility of this with a local organization that is familiar with the laws in Wisconsin.
If I am reading the law correctly, the only ones allowed to teach homeschool students in WI are the parents of the student or the parents of another student that is registered as a homeschooler.
DCK2003...please stop making stuff up and presenting it as facts.
ETA: That is a survey of 7,306 members of HSLDA, a Christian organization and no where does it state that 76% are evangelical Christians (although I haven no doubt that the membership of HSLDA is made up of that that many). It states that 76% of those survey homeschool for religious reasons. However that is in no way a reflection of the majority of homeschoolers in the US.
It is estimated that there are over 2.5 million children are being homeschooled in the US. Those 7,306 families surveyed are only a tiny fraction of those who homeschool in the US. Do you seriously believe that 7,306 families in a Christian organization are a good representation of 2.5 million in the general US population?
A recent piece on CNN stated that only 1/3 of homeschoolers cite religion as the reason they homeschool. At one point I had similar studies bookmarked but lost them in a hard drive crash. I will attempted to find the studies and post them in the morning.
ETA: Back to the topic on hand. While I am not in WI (and I do not believe anyone else who commented is either) I don't know a single homeschooler who has not used a tutor, private classes or co-op. I also know of several evangelical churches who offer classes for homeschoolers. Not that religion is relevant but since DCK2003 thinks it is I thought I would throw that out there. Even HSLDA acknowledges that many f their member do because many of their "alerts" have been concerning equal rights for homosexuals in which they claim that granting equal rights would force their members to hire child molesters to teach and tutor homeschoolers students. If WI law does allow teaching and/or tutoring, I really think you won't have a hard time at all especially considering the topics you mentioned. We could have used you last year at our co-op when the wild eatable plants teacher quit after 2 classes (according to him he didn't realize how far he would have to drive to get to the co-op).
ETA: Our local library has a bulletin board in their homeschool resource area for tutors to post their services.