We have generally observed that it is easier, and much less expensive, to prevent a problem than to fix one. (This applies to most things in life, not just legal issues). Since purchasing real estate is one of the most financially significant transactions most people ever participate in, we recommend having an attorney right from the start, before you sign a document. An attorney will help you understand both your rights and obligations, and make clear the implications of provisions in a contract that may seem harmless but could end up costing you a lot of money.
An experienced Wisconsin real estate attorney will not have to spend an excessive amount of time on a typical transaction. Considering the cost of the transaction (and what you could lose if something goes wrong), having an attorney's advice throughout is an investment, not an expense.