I'm glad you specified your state, because different states have different licensing requirements when it comes to certain business activities. The Michigan Economic Development Corp. has a list of the businesses that require a license. Note that "auctioneer" is among them. Additionally, depending on what you will be auctioning, other licenses may be involved as well. It's best to speak to a local business attorney who deals with auctions to determine which of these licenses will apply to your situation.