Me and my friends decided to stay in Charles and Amelia's apartment for 4 nights, it was easy to find, it's very well connected with the metro, and although it isn't very central, (take in mind that it's 30/40 minutes away from the main tourists areas, using the metro) the area is very nice, very calm, near the S. Martin Canal and it has everything you could need: little cafes, supermarkets, shops etc., in a way it was like living as a real Parisian.
We were 5 people, it was a bit small for us to be honest, I think it's more suitable for 4 people and 1 child, or just 4 people.
The apartment was apparently clean, and modern, it had everything you could need during your stay: dishwasher, washer, microwave, fridge, shower etc.
The only thing I really didn't like was the fact that the pillows were yellow, and the mattresses a little bit dirty, I would really suggest to change them.
We couldn't figure out how to work the microwave even tho we tried to turn it on multiple times, we don't know if it was broken or we just couldn't figure out how to turn it on.
After the second night of our stay the heating stopped working, and it was freezing, hopefully they can fix it some time soon.
All in all it was enjoyable, Charles is really kind and always ready to help.