Is it too late in the year to start mint? I have a very similar situation to the OP; live in an apartment in SE Michigan with a window/balcony, but near trees. I'm assuming it'll have to come inside around mid-October.
Mint is like a crazy weed. It'll take over your garden given half a chance. It survives mild (UK) winters, but probably needs to be established before it will do that. So you might want to look for advice and maybe start it indoors for the first winter.
I did make a great discovery this year: chocolate mint (mentha piperita). The leaves taste like minty chocolate (you really have to try this -- you won't believe it until you do).
Also, I've heard conflicting reports about growing mint indoors over the winter; some sources say that mint needs to die down in the winter and won't survive year-round growing, but others don't mention it. Should I just plant two pots, one indoors and one out?
I've always bought it in pots, not tried it from seed. The pots are really cheap anyway (like $3 equivalent). All they need are watering, and if they die off, just get another pot ...
I did make a great discovery this year: chocolate mint (mentha piperita). The leaves taste like minty chocolate (you really have to try this -- you won't believe it until you do).