I wish I didn't have to! Some cities in the US just don't have good options, or the good ones are just very expensive! I'm not trying to be cheap, far from it! When I head into a new city, I like to have something lined up before I go, and sometimes agencies are the best bet. Again, not my first choice!
Happy to take suggestions for Minneapolis if you have any? ;)
There is 1 post on this forum on that town, and that person suggested using SeekingArrangements.com - which I have not tried yet, so I might go that route.