We really liked our stay at Alexandra’s airbnb. She wasn’t in Madrid but Rodrigo made the whole process quite smooth. We had some trouble finding the house (play close attention to the guidelines they give of arriving) and then later on how to turn on the cooler, but Rodrigo helped us with both. Also, they were accommodating with our other requests related to check in and check out too.
The house is great for 2 ppl and maybe a family of 3 as well. But for 3 friends, it might seem smaller. They have made great use of the small space they have though, so I have no complaints.
To go to the city center, you will have to travel a bit, but the bus stop is right in front of the house and the metro station is 10 minutes away on foot.