This is the quintessence of AirBnB, meeting the private host in person - it's been a while that this happened to us! And if your host is as cultivated and educated as Brice, then you got a lucky strike. His communication was very proactive from the start and he received personally (stunning night view of Sacre Cœur from his sitting room, he lives in the same house). Brice is a filmmaker, and storytelling he can, he shared interesting histories about the place, and I could not resist his library (art books, cinema books, novels, the book he turned into a film, unusual Paris guides, all mostly in French and English, a little treasure trove, even graphic novels, my kindle remained closed). And throughout the stay he kept asking if all was good, if anything was needed, so I felt quite pampered.
Now the studio is larger than it looks, it could easily accommodate a couple. The kitchen is decently equipped, with some basic food supply and all necessary cooking utensils. The bathroom has enough space for a tub, the toilet and a washing machine and a real window. The living- and bedroom has a solid table with real chairs, a small bureau for your laptop, a comfy sofa and a mattress pile, and an expendable bed big enough for two. Everything is in quite good shape and clean, and indeed a designer's den with unique pieces. Even the windows are special. They overlook a very quiet yard btw., no street or traffic noise. It's the walls that are thin, so you can hear the neighbors talk, but there was no wild party during my 10 days' stay. However, in the main courtyard, a construction site has just been completed, and scaffolding has been taken down. In the backyard on the other side, a wall was demolished by the hammer in the flat vis-à-vis which made "home office" a bit difficult (they works should be all done by now).
Finally the neighborhood, which is called faubourg (suburb of) Montmartre. In walking distance you have the famous boulevards in the north and lively smaller streets all around you, with charming shops and local supply. St. Georges with it's three (!) theatres is no 10 minutes walk away, St. Lazare and further down the famous Opéra Garnier and Grands Magasins reachable within 25 minutes (if you don't get stuck on the way in one of the many charming cafés or brasseries). Oh and are you vegan? There's probably one of the best vegan restaurants just down the same road, as well as a vegan & raw food place, at least 2 vegan bakeries and a vegan burger place literally round the corners.
To summarize - a charming host offering his lovely place, I can but only recommend!