I do the taxes for my brother in law. He doesn't make enough income to need to complete a federal return. Is there a way on turbo tax to just do a Michigan return?

No.

 When you use TurboTax the information flows from the federal return to the state return.  You cannot use TT to prepare a "stand alone" state return.  Try going to your state's tax website to see if you can file there.

https://ttlc.intuit.com/community/state-taxes/help/how-do-i-contact-my-state-department-of-revenue/0...

Or—-Use this IRS site for other ways to file for free.  There are 8  free software versions available from the IRS Free File site

https://apps.irs.gov/app/freeFile/

No.

 When you use TurboTax the information flows from the federal return to the state return.  You cannot use TT to prepare a "stand alone" state return.  Try going to your state's tax website to see if you can file there.

https://ttlc.intuit.com/community/state-taxes/help/how-do-i-contact-my-state-department-of-revenue/0...