Ohayo Gozaimashita Sukotto! I really hope you achieve your goal and get to have your stay in Japan! I would definitely suggest to find someone in Japan beforehand who would be willing to help you learn Japanese,and you could most likely teach them some english as well.
As c8lor suggested, finding a more rural area to stay in would be better. Begin to form friendships with the people there, and so they will know you day to day. There will be a greater chance of you attaining a well paying job in a big city, but the cost of things will be much less in small towns/cities.
I really hope this will help in some way!