Lovely/spacious apartment - what you see is what you get; great location but do note some areas:
1) Great location, right next to Gare du Nord station, easy access to trains, RER, Metro, Eurostar. But this meant cars waiting to pick up friends/customers will wait right downstairs, and the inevitable honking especially during peak hours. Not a major issue for us.
2) Toilet paper, shower gel, laundry detergent supply especially if you are staying a week or more. There is a small bar of soap provided but no shampoo. Couldn't find extra trash bags as well, but we made do by clearing the big items of trash on a daily basis.
3) Some areas in the home were quite dark, especially at night. The master room (where my husband accidentally broke the only lamp - see point below), the corridor leading to the toilet esp. A blown lightbulb, easily replaced. But don't think you are coming to Paris to go hunting for a replacement bulb?
4) My husband accidentally broke the only lamp in the master room, and to cut the long story short, we decided to make good by simply leaving cash behind since it was a common IKEA lamp that is still being sold for 9.99Euro (we did some research online). All this was communicated to the owner, but he took a while to get back. He was very nice about it, telling us not to worry, which we appreciated. But there might be some misunderstanding and hopefully not too much bad feelings, as he made a claim via Airbnb which we rejected since we felt we already made good the damage.
5) We were also caught in a terrible heatwave midway through our stay in Paris - it was easily 33 deg C in the middle of the night with no wind, one particular night. There was no fan, and no aircon in place, so it was a long night. No fault of the owner, but be warned if you are coming in summer! Feedback about this given to the owner as well.
6) Would have been very useful if simple English instructions are given for the appliances for eg. washing machine, dryer, oven, etc. I managed to get them working using common sense and (SENSITIVE CONTENTS HIDDEN) Translate as everything was in French.
All in all, we enjoyed the stay, but would have benefited from the insights above.