Residents of Grand Rapids are taxed on all income received regardless of where it came from, same as the federal return. See the Form GR-1040R instructions WHO MUST USE THIS FORM / Full-year resident and the TAXABLE INCOME section after that. So income earned in town of Wyoming is taxable by Grand Rapids for Grand Rapids residents.
https://www.grandrapidsmi.gov/files/assets/public/departments/income-tax/files/individual/2017-form-...
