You could do a search on "Flint MI white pages" and that should get you to an online phone directory - if they are listed in the phone book, they should be there.
Is this person a property or business owner? The city has a website with various databases, go to cityofflint.com, if they pay property or business taxes, there will be a record.
Also, if they belong to a particular faith or church that you know of, maybe you could try churches.
If this person has an unusual name, try googling the name, plus Flint, or Genesee County, or something like that. It's amazing how many people have left some sort of trace on the internet!
I live in Flint, I could always go into my back door and yell their name real loud.
That probably wouldn't work, though!