There is no elevator in the building and if you are booking level 2 you have to carry luggage up the staircase. The check in instruction only stated JR line but no Subway. To go to this airbnb via Tokyo Subway you may go to Higashi-Shinjuku exit which is the nearest to Shin-Okubo. So far the amenities considered rather complete so you do not need to bring too many things during your stay.