The money should be the least of your worries if your going to Japan to work.
You'll most likely be working on a Military base. Which means you'll be given SOFA status. SOFA status agreements are very strict! The company (Such as Americable Intl. Japan, Inc. and Walker Enterprises) help you get your SOFA agreement when you get there but then "Use it as colladeral" against you have it!
The company fire you "at will" regardless of your "contractual agreement" and they can strand you in Japan!
I highly suggest you make damn sure you have a "return flight ticket home" before leaving.
As for the living expenses in Japan? It's quite expensive to live there.
Your looking at a minimum of $900.00 US to rent a 2 bedroom on the Cho. That does not include heat/Air and I do not mean Utilities! Most Cho-homes do not have heat or air conditioning in them. You ave to purchase a karoscene or electric space heater.
Or a combination Air/Heater unit and have it pofessionally installed.
Electricity is SKY HIGH there so I highly suggest Karoscene space heaters.
Food is very expensive. Unless you get Military privileges for on base shopping.
Anyway, I would not go back to Japan working as an Employee for less than $60K a year (tax free) or 100K a year min. for a sub.
What else would you like to know??????????
