I currently own a duplex in Grand Rapids near downtown GVSU.  I am interested in adding a bedroom in the attic to get more rental income and I am having a hard time finding requirements for it to all be legal.  

The duplex is mirror image and one side of the attic is already finished.  During my last certification the inspector said something to the effect of "this is kind of a cool room, but you can't use it as a bedroom."  It has a closet, smoke detector, overhead light, multiple electrical receptacles, and two sets of windows.  Due to peaks in the roof, square footage is difficult to measure, but I believe it to be over 100 sq ft at areas with the ceiling over 7 feet.

It is currently unconditioned space, so I was thinking of adding baseboard heaters.  I would like to do that on the mostly completed side and rent it as a three bed instead of a 2 bed with bonus room.   Once that's finished I'd like to finish the other side in the same way.

Is there a good resource describing what will be necessary to make the attic space legally qualify as bedrooms in Grand Rapids?

I looked this up about a week ago. I cant find the document or reference I saw but you could just Google grand rapids building inspection or housing requirements and find something.

Call the city and ask. They are usually more than helpful with me. I've even had the inspector come out free of charge to talk plans...maybe it was just my luck depending on the inspector though. 

six one six, four 5 six, 4100 for the city. 

So what did you find out?  Legal or not legal? 

I found out rents have gone up enough that I could get what I wanted without messing with an attic bedroom. 

Well, that works too!  Congrats!