A lot of homes in Northern Wisconsin have wood siding. With wood siding comes a need to maintain it. If wood siding has not been properly maintained it will start to cup, rot and stain making your house look old and unkept. If you are buying a home, the siding should be inspected closely.
Another material to look closely at when buying an existing house is the roofing material. Shingle quality varies by quite a bit and some shingles are known to fail before others. Some have longer, transferrable warranties when other's don't. If a roof has started to fail, you could be looking at a large expense in the near future.