If we're planning on staying in the more affordable places along the way, like "Comfort Inns" and motel 6. Do we have to book those places now?? Same with a rental car??

Where are you going, and are there any big events going on in that area at the same time? If not, you're probably safe, but...as long as you know where you're going and when, why not book everything now, and cancel later if you have to? With the rental car in particular, prices can change and you might as well lock in the best price you can. If the price drops later, cancel the original booking and get the new price.

Of course, this is all assuming you book hotels and the rental car through sites that allow you to cancel with no penalties.

No

Where are you going?

It's definitely not too late, as long as there's no huge event (car race, marathon, festival) going on. I normally wait until three months out to book airfare because the bargains tend to be better, as airlines and hotels are trying to fill empty seats/rooms.

No everything is booked.

I booked a comfort inn in chicago, great location, so it's not cheap. Quikbook gave the best price.

Faina, How did you know OP was going to Chicago?
"Along the way" to where?

Schnookies, dear, is this a joke? Why do you refuse to let us know where you are traveling?