@Zach Romashko
I'm currently shopping in the Mankato market as well. You are correct that they are strict about the 25% rental concentration rule and purchasing in a place that either already has a license or you know you an get one is key. Another rule you may not know about is that if your address is greater than 30 miles from Mankato, you are required to have property management within a 30 mile radius. You can find more details on the city website. I haven't looked into it too much but I'm concerned that rule might drive the price of property management up (especially with the bigger property management companies in town).
I agree with @John Woodrich that deciding where you'd like to invest and who your target market will be will be a decision for you to make. There are opportunities for student and non student rentals.
Finally, I was talking to a real estate agent last Friday and he mentioned a few duplexes that may be coming on the market for the $110-125 range. There are opportunities in town, you just have to find them!
Good luck in your search!