We stayed at Julien's home for 8 nights with our boys ages 6 and 7. Julien has put a lot of effort into updating the home that was built in the 1600s. It is a romantic and cozy space that would be perfect for a couple or a group of young adults visiting Paris.
The area is a busy, up-and-coming neighborhood called Le Marais. It is home to the gay community and a lot of younger adults. The area is going through gentrification and there was a lot of construction to update buildings. We felt very safe walking around and getting place to place. There is a super market within walking distance and a small but very accommodating kitchen to save money on meals. There also is a lovely bakery called Legay Choc that offers delicious breads and breakfast (but also has some colorful baguettes hanging in the window). The home is very short walk to the metro where you can get anywhere in the city. It is a walking distance to Notre Dame where our kids would play with pigeons in the evenings.
They do own a cat and there was some hair, I am allergic but it didn't bother me too much. There is no A/C but opening the windows seemed to manage the temperature well enough in August. When the windows are open, the courtyard can be loud if people are talking in it. However, much quieter than if it opened to the city streets. With the windows closed you cannot hear anything. This was only an issue one night out of the 8 when some neighbors were outside until late.
Overall we enjoyed our stay, and it was a good price and a romantic quiet little apartment in a busy city.