There aren't any house shares, like they sometimes have in Tokyo, but if you are lucky you may find someone looking for a room mate. As I said in my pm
though, if you want somewhere cheap, quite a few of these 'Guest Houses' have sprung up in recent years, for 1,000yen per night. Am not sure, but
it may involve sharing a room, but I will check into it. There are also quite a few monthly 'mansions'(apartments), where you can rent by the month.