There's a big difference between seller financing using a mortgage and a note, and selling on a land contract. Land contracts in Michigan are only allowed to be written by an unlicensed individual if the seller had lived in the house as their primary residence. If the house was an investment property then the land contract must be negotiated and written by a licensed loan origator, attorney or real estate broker who is involved in the sale. Terms, interest rate and any fees are also contolled by state lending laws along with disclosures. Contact a real estate attorney or a local licensed loan originator to keep your financing compliant and all parties safe.
You should definitely call an attorney to draft the land contract and have a reputable title company hold the deed in escrow for the duration of the contract. I would recommend attorney Nathan White in Royal Oak.