Hi mcrich -
There is another thread with extensive discussion on this topic, and many there (including me) read the MRTFA as protecting any farm operation that is both commercial and that follows good management practices (GAAMPS). There is no size limit to the farm, and no time limit as to when the farm was started. If it is commercial (e.g., by selling an egg) and if it follows good management practices, MRTFA protects, and trumps any local ordinance that aims to impede your commercial farm operation.
VikkiP, who successfully went to court over this issue, posted this link as a very easy description of the MRTFA from MSU:
http://www.animalagteam.msu.edu/uploads/files/20/Tech%20Bullitin%20Land%20Use.pdf
Be sure to look at page 2, which I think will convince you that you're protected if you sell any products from your chickens, and are (or become) compliant with GAAMPS.
I also encourage you to go to that other MRTFA thread, because it looks as though someone else may be gearing up to fight this battle in Ypsilanti. http://www.backyardchickens.com/t/182280/michigan-right-to-farm-law-what-does-it-mean/470#post_8390924
Best of luck.