Thinking of moving to Japan?
If you are an engineer working for Toyota or Boeing and being sent abroad, rest assured. You will live like royalty in American-style housing set up by your company through a relocation agent. The rents on two- or three-bedroom American style apartments or homes in expat towns of Nagoya or Tokyo run in the $2500-7000 per month category.
If you are an English teacher, you will probably be closer to the $300-600 per month category. For this price, you can stay in a nice, clean "1K" apartment (explained below), but it will be small, with only one or two rooms, a kitchen, and a (often separate) toilet and shower/bath area. The area of the apartment will be somewhere around 250-350 square feet, which means the whole apartment could fit inside the master bedroom of a lot of American homes.
First-timers in Japan will have everything set up for them by their company. Often, an English school will keep an apartment constantly rented (and maybe partially furnished) for that school. Whoever happens to be teaching at that school at a given time lives in that apartment (which means no key money or deposit). If your company provides this kind of housing and subsidizes it, there can be perks. The building won't be as clean or new, but you'll get away with $100-200 rent per month. On the other hand, if your company "provides" this kind of housing but still makes you pay $500+, be a little wary; the place should either be fairly nice or they should offer a reasonable explanation of why you can't choose from multiple locations. Often this will boil down to guarantor issues.
If you have more experience in Japan, or if you are moving from one job inside the country to another, you might get the thrilling experience of choosing your own apartment!