This apartment is both charming and user friendly and located in the heart of the Marais district. The building itself dates to the 14th Century. The apartment overlooks a busy and lively street, but closing the windows facing the street guarantees quiet. The apartment is close to major transportation arteries, including Metro, Bus, and RER. But it's also possible to walk easily to many places, for example to Notre Dame Cathedral (about 15 minutes) or even the Louvre Museum (about 20 minutes).
Xavier is a kind and thoughtful host. He answered our questions promptly and with a great knowledge of what's in the area.
There were four of us staying in the apartment: my two daughters, my partner, and I. We did not feel cramped after staying in the apartment for a week.
We did not have a car while in Paris so cannot comment on how feasible it would be to have one there. The streets are quite narrow and I would recommend using public transportation if possible.