100,000 yen/month in Tokyo is pretty tight. I spent that amount over the course of 3 evenings last year. :)

Of course it's possible but it'll require some major discipline on your part and some careful planning. You won't have much of a social life either since everyone loves to go out.

Do you live in a country which participates in the working holiday program? If so, that might be a better alternative.

This should give you a basic idea of how much essential things cost:
Cost living in Tokyo - cost of living in Japan

To give you another perspective, Tokyo is one of the costliest cities to live in - definitely among top 10, as per wikipedia and youe monthly budget is ~1000 USD. So I'd think it's going to be tight. Even if you share apartment, rent and cost of traveling is quite high.

It may be a bit easier if you choose a different city in Japan.

Unfortunately I don't have that chance.

Thanks for the all the links and replies in this thread. They gave me some good options to consider.

Another question, do you think these programs have a better effect on a person with a beginner level or intermediate/advanced level in Japanese?