Incoming Keio exchange student is unsure where to live...

Hello all!
So, in September i am doing a one year exchange at Keio University, but I have been having trouble deciding where to live. I have a lot of family living in various parts of Japan, including Tokyo. My cousin lives in Shimo Kitazawa and after visiting him i fell in love with the area. If i could pick anywhere to live, that would be my first pick. But my question is this: Is that too long of a commute? Its only a couple of stops from Shibuya which is on the Yamanote sen, so i originally thought it was okay, but i am now second guessing my plans.
Any other thoughts? Cool areas that are closer to Keio? Setagaya in general is on the cheaper side of Tokyo so that was a plus too... In any case, I'm looking forward to some feedback! Thanks!

Which Keio Campus? Mita?
Setagaya didn't used to be considered "cheap" unless you're comparing it to Aoyama or Den'en Chofu or something. I used to live near there and I love that area as well. Plus it was convenient as you could easily get to Shinjuku or Shibuya from there. From Shimo to Tamachi is not bad at all by Tokyo commuting standards but you're right in that it's not as convenient as taking a single line. If you consider getting a 50cc scooter, your transportation concerns would be alleviated quite a bit. It's only about 12 km by road.
Or consider something along the Tokaido/Keihin-Tohoku lines towards Kawasaki. If your commute doesn't align with morning rush hour it wouldn't be too bad in terms of the crowds.

Exactly what mdchachi said. If only I had a commute as short as Shimo Kita to Tamachi! As a student you probably won't have to commute during peak hours all the time. The journey into Shibuya in the mornings will be very crowded, but the Yamanote line should be OK - lots of people will be getting off the train at Shibuya before you get on.. It will also be worth getting yourself a season ticket for the train.
I occasionally go out in Shimo Kita and it's one of my favourite areas of Tokyo. I've you've found a part of Tokyo you like and you've got a cousin living there, I'd go for it.

What advice does Keio offer? Maybe you have no choice at all!

Hi @ianchan
May I know if you are based in Mita/Hiyoshi/Yagami or other campus?
thanks.