Out of all of my Parisian experiences, stay with Frédéric's place tops the list.
The apartment is very comfortable and clean, lot of painting and sculptures.
Also, it is very central and close to a big station: Gare de Lyon, which makes you very easy to explore the city.
Our hosts are very friendly and shared me many useful tips, such as, the most delicious bakery in the city and the best way to explore/enjoy the city.