Forget Champaign. Go to Ann Arbor, MI. You have all the same benefits as Champaign --- a walkable/bikeable city, a huge reservoir of engineering talent, a reasonable cost of living --- but you also have Detroit Metro if you need to pick up freelancing work. Detroit Metro has plenty of BigCo employers outside the big 3.
I lived in A2 for 4 years, and while I think Chicago is a better place to start a company, I have lots of good things to say about the place. I have almost nothing good to say about Champaign, which is a bleak, depressing place vindicated only by its proximity to Chicago.