[vulgarshudder]

As mmm has said, I wouldn't worry about not being able to save. I live in the middle of Osaka, on faaar less than a JET, paying more in rent, and after bills and stuff (a hefty cell phone bill for one) I still have about $1000 for play money or saving.

However I'm from London, and Osaka seems CHEAP to me.

Cheapest places to be will be the countryside. Not only the cost of living, but also there won't be so much to do than if you were in Tokyo or Osaka.

However Jets placement choices...well be flexible. You say you want snow so Hokkaido, you could end up in Nagano.

So don't worry about it, just apply and hope for the best.