[Hatredcopter]

If you want to go to Japan at 18, you must attend a university.. you pretty much have no choice on this matter, because of visa issues. You need a working visa to live and work in Japan, but getting a working visa requires a bachelor's degree. The only other way to live in Japan prior to getting a degree is by attaining a student visa - hence enrolling at a Japanese university.

Here's where the problem comes up. You need to be fluent in Japanese to attend a Japanese university. However... there are a VERY small number of universities in Japan that conduct a good amount of their classes in English (Temple, Sophia, International). These universities would be your best bet, although tuition is quite expensive. I don't know if there's any other universities in the country that could suit someone who doesn't have an advanced grasp on Japanese (i.e., completely fluent and literate).

Like in the US (and pretty much everywhere else), many Japanese universities have dormitories.. so housing would be covered.