You got no replies, so I will give you some feedback. I travel to 2 games per year and rent an airbnb. I am a season ticket holder so that is not an issue, but I doubt that you will need to pay much over face value for the Northwestern Game. Getting 5 together may be a challenge, and may cost more. You may also be able to get tickets for that game when they have an open sale, but they will not be great tickets. If you are planning to tailgate which I recommend that you do, you will need a parking pass. You will pay between $40 and $100 for this for a car.
I have been using Airbnb (or VRBO) for about a decade. I have never rented the same place twice. I have had mostly very good experiences. For a house that is within 10 miles and has enough beds to sleep 4 or 5 adults, you will probably spend $900 - $1500 for the weekend. (Prices vary greatly by game. Ohio State is very expensive, Central Michigan not so much.) Rule number one is to make sure that you and your friends have the place to yourself. You don't want a place that is renting out a separate room or apartment. Make sure that you understand the bed configuration and the bathroom situation. That is key to a happy weekend. Look for reviews. No reviews is not necessarily a game breaker, but I would make sure that you know what you are getting into. Also check on parking. If you are coming with multiple cars, it can be a problem. Many airbnbs are in townhouse complexes and only have 1 or 2 parking spots.
Good luck and enjoy.
