[Nyororin]

There is high demand - and an endless supply of people wanting to make it big as a model in Japan... Something that translates to "lots of options, most desperate and willing to model for almost no pay to get a chance".
The endless supply of hopefuls are already IN Japan. I have honestly never heard of a modelling agency sponsoring a model and bringing them to Japan - let alone an amateur. If they do bring someone in, it`s someone they contract from an overseas agency.

If you do want to pursue it, you`ll need to already be in Japan and to have a professional portfolio. That will give you a chance to be listed at some agency... But that guarantees nothing other that your picture will show up in a large catalog of "on call" models. If no one chooses you, you`ll be out the registration fee and the cost of the portfolio.

In my opinion, you would be better off working for what you can and looking into regular student loans. There is a chance that you could make a fair amount of money working part time teaching in Japan, something that could be saved and applied toward loans when you head back home.