The host was not available to check us in, but he arranged for the cleaning lady to meet us to give us the key.
We arrived early, while she was still cleaning, so she asked us to come back later. We were able to leave our luggage in the home while we went out to eat. When we came back, there was a strong smell of air freshener. However, everything was clean and everything we needed was there. The only thing that was a little concerning is that the washing machine leaks water.
If the wifi does not show up, make sure the white box next to the TV in the living room is turned on. The host left instructions for us to turn off all the extension cords when we check out, and the white box might not have gotten turned back on from the previous guest.
According to someone who lives in Paris, the area is dangerous. However, in our experience, it was just an ethnically diverse place with lots of different people and lots of different kinds of restaurants. There was nothing dangerous even when we took the train back at 10pm one night. If you don't look stupid, rich, or confused, you should be ok.
The first floor is a Chinese restaurant. You have to go into the building and up the stairs to find the apartment.