Highly recommend: I stayed at one of Beatriz's Airbnb rooms in her 2-bedroom apartment for one week and highly recommend it for any travelers who want a safe and quiet place to sleep, accessible to attractions by metro, and some even by 15-20 minute walk.
The host: Beatriz is a kind, communicative, and accommodating host. She gave me some welcome drinks and snacks, which was very thoughtful of her. It would likely be easier for you if you have the messaging application of her choice during your stay should you need to reach out to her to ask about anything. I had my itinerary already planned out so I mostly just needed a place to sleep, and I appreciated the privacy.
The room: I stayed in her bedroom that had 2 small size beds and access to a private bathroom in the hallway. The bathroom is used privately and is not attached to this specific bedroom. Beatriz also rents out her other room on Airbnb FYI - in case you are not comfortable sharing a 2-br apartment with another stranger. When it is not rented out, you would be sharing the apartment with the host herself. There room and bathroom are extremely spacious. Beatriz added convenient touches to the room, including a portable clothing rack you can use, a small table, and light switches next to the beds. She can provide a fan as needed.
The bathroom: Bathroom is also spacious. She provides towels, and she also leaves a large body wash and a hairdryer if needed.
Check-in: Beatriz was very accommodating. My flight was scheduled to land in the AM, and she was willing to allow me to check in as early as 7am (I ended up checking in closer to 8-9 AM local time). Check-in was very easy.
Communication: Beatriz was very communicative leading up to my stay and during. I was surprised, however, to learn that she does not speak English, as the listing showed that the host can speak English in addition to Spanish. She does have a translator friend, and she was able to contact him when I had a question about using the AC (it was 90-100F during the beginning of my stay in Madrid). So, all in all, communication-wise worked out, but it would have been nice to have the listing accurately reflect the host's spoken languages.
Cleanliness: The apartment was very clean, everything from the kitchen, living/dining room, bedroom, bathroom, to the main building, the courtyard of the apartment complex, etc.
Accuracy: The listing is very accurate with two caveats mentioned above: host languages + the bedroom being one of two that are both rented out on Airbnb (sharing apartment potentially with a stranger and not the host)
Safety: 10/10, felt very safe as a solo female traveler. The apartment is in a locked and gated apartment complex.
Location - neighborhood: It is located in a very residential part of Madrid, Delicias, and is both safe and quiet.
Location - accessibility: It is easily accessible by metro, a quick 3 or 5 minute walk from two different stops to the city metro. It is also easily accessible to/from the MAD main airport via the Renfe stop (C1, C10 - this is much cheaper than taking the city metro when going to/from the airport). It is also <20 min walk to the Madrid Atocha station, where you can easily take the train to do other day trips via the bullet train (AVE) to places like Toledo, Avila, Segovia, etc.
Location - convenience: There are also convenient supermarkets like Dia, Mercado located <5 minute walk from the apartment. These stores are open later and were very convenient when I needed to buy toiletries I forgot or some quick snacks (e.g. yogurt). It's also located to a more traditional market that's only open during the day time (Beatriz will recommend to you if you ask)
Value: Great value for the price, though I did go off-season.