How much time should I plan to stay in temporary accommodation before finding a more long-term one?

Hi everyone,

I'm going to Japan in a few months with a WHV for a year and wanted your opinions on how long it should take to find and actually move in a monthly rental (東京 area) after arrival.

I'm not targeting a particular location/area in 東京 and won't be too picky as long as it's not too far from a train/metro station.

I'm sure I can find something decent within a week, but I'm more afraid of the time between me saying "yes" and me actually getting the keys. I've looked at the prices for short-term accommodation, and concluded I really don't want to pay that price for too many days haha…

Would you say one week (or like, 9 days to include two weekends) is enough? Or should I instead make a reservation for two weeks? Of course, I could always extend my temporary accommodation elsewhere (hotels…) if needed, but the more I anticipate, the better it is for my poor wallet.

Thanks!