For the accommodation part of your question, I believe one of the cheapest, if not cheapest place to stay in Tokyo is a chain of backpackers hostels called 'Khaosan Tokyo.'
The rooms are the tiniest things you can imagine, literally the bed, a space to put your suitcase, and that's it. All facilities including toilets and showers are shared.
But it does have many good points, like free internet access, free baggage keeping etc. And of course, the price.
Rooms vary from shared dorms if you don't mind being in a room with strangers, or private rooms (I
think you only have the options of 'double' or 'twin' bed rooms though, but I'm not sure) if you prefer privacy.
Price example: For a private, twin bed room (it's a bunk bed), it only costs 2500 Yen per person per night
To look up specific Khaosan branch options, and prices for other types of rooms that may suit you better, this is their website:
khaosan Tokyo Guest House ::Backpackers Hostel in Tokyo, Kyoto, Fukuoka, Beppu::
