There appears to be some confusion on your part here that is not clear based on your question. First, you already have a private, closely held corporation, unless you created a public corporation and had an initial public offering when you opened. I seriously doubt you did this or you would know it already.
Are you trying to find out if you have an entity that has pass through taxation? If so, this has nothing to do with selling your shares. You elect this type of tax treatment when create the entity and you can only do this with an S corp. or an LLC.
All this said, as was previously mentioned by the other attorneys who have responded, you can sell your shares privately as long as your disclosers and or PPM's comply with SEC filing requirements, or the exemptions thereunder, as well as the State of Michigan Blue Sky laws. There is NO WAY an attorney can talk you through this on the internet - far to complicated and expensive. What you need to do is hire a good corporate lawyer who can handle these matters and can also clarify your questions. Good Luck.
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You have no obligation to sell shares to anyone publicly. You may sell shares privately provided you comply with federal law and the law of any state where you are selling the shares. These laws can be quite tricky and you really should speak to a lawyer before selling (or offering to sell) any shares.
I would also suggest you read a book or article about corporations, as your understanding of what it mean to own a corporation seems limited. You have ongoing obligations and you need to get a handle on those.
I don't think I would opine here only because I am not exactly sure what you are trying to accomplish at large.
As my colleague aptly notes, this can get complicated, so I suggest that you discuss it all over with a lawyer in private. You may want to call several first for a free phone consult then pick the best fit to work with.
DISCLAIMER: this is not intended to be specific legal advice and should not be relied upon as such. No attorney-client relationship is formed with the law firm of Natoli-Lapin, LLC on the basis of this posting.