Once you arrived in Japan, lodging would be essential. Therefore, you should make clear that whether the school you want to enter has domitory or not. Similarly, you should confirm that how much rent you should pay, and how many people will live in ne room. Furthermore, you also should check how much it cost from domitory to your school.
However, there are very few domitories which is both cheap and near to school. Especially in Tokyo, it is difficult to find a domitory which is not only cheap but near to your school as well. It is better to live in domitory attached to your school for the first year you come to Japan, and find you own lodging after second year.
On the other hand, you have to prepare for the case that your school do not have attached domitory or its domitory cannot accommodate to all the registered students. In these cases, you should confirm whether your school will help you find lodging or not. In addition, you should confirm that whether the school will provide you with temporary domitory before you find your own.

If school could not provide you with temporary domitory, you should think where you should live. As rent contraction always stipulates that people other than contractors cannot stay, it is impossible for you to stay in your friends’ lodge. If you do that in silenct, you and your friend will risk being driven out by owner. Therefore, before staying in your friend’s lodging, you have to ask permission from the owner of that lodge.
If it is impossible for you to stay at your friend’s room, you could make use of youth hotel, weekly-mansion, or guest house.
In the case of youth hotel, it cost 4,000yen for one day stay. Before coming to Japan, it is better for you to apply to be member of youth hotel organization and make reservation at the same time.
In the case of weekly mansion, bed, furniture, cooking items had been installed. There are both single room and twin room. If the weekly mansion is near the centre of Tokyo, it may cost 100,000yen per month. If it is in the suburbs, it cost nearly 70,000yen per month. Rent will be counted for per day, you just pay for the days you stay there.
In guest house, bunk beds had been equipped in one big room. There are nearly ten person stay together. In the centre of Tokyo, it costs 30,000 to 40,000yen per month. Rent will be counted for per day, you just pay for the days you stay there.
Besides, there are some cheap business hotels in Japan. For example, Toyoko Inn. 5,500 yen for single room and 7,600 yen for twin room. Sometimes breakfast will be available.

This is Toyoko Inn’s homepage address.
http://www.tokyo-inn.com/