In reply to dunnyg:
You should be able to rent a room in a house for around $400-500/month quite easily. Best best is to check the classifieds at the back of the Rocky Mountain Outlook (free paper), also the Canmore Leader. Also try kijiji.ca - there's a Banff/Canmore section. Damage deposit is usually one month's rent but you'll get it back if you're good
Rooms are often (but not always) unfurnished. The Canmore thrift store (near the high school) sells cheapish mattresses (and everything else you can think of), or check kijiji again. Or sleep on your thermarest.
Alcohol is expensive, both in bars and from the store. Food is cheapest at Safeway or Sobeys. Cheaper supermarkets in Calgary if you can get in with a vehicle to do a big shop.
Save any drinks bottles, you get money back from them (admittedly not a lot, but it helps). Hitching into Banff/Sunshine is easy. Into Kananaskis not so much. No public transport to speak of. Really worth having a vehicle if you can afford for getting out climbing/backcountry skiing. Petrol is cheap!