View: https://www.youtube.com/watch?v=j5bVWzTyJ7E
It's the sleeping arrangement of choice for Nippon truecels.
There are much nicer ones than the one shown in the video, there are some PC Cafes that have capsules as well.
As for luggage, you should carry as little as possible. If need be use the storage units.
Japan is actually pretty reasonable as far as expenses go, even hotels aren't all that expensive.
Food is dirt cheap and quality ready-to-eat meals are available in every convenience store.
Think English teaching is copium if you have a heavy accent.