I enjoyed my stay at Yan's basement apartment. It's exactly as the pictures depict - it's clean, and spacious, though there is a step into each room so folks with mobility issues may find that to be a hassle.
The kitchen is well equipped with all the basics I needed (and I cook a lot). I could hear the neighbors upstairs intermittently, but they don't clomp like elephants and they kept the same hours as me (asleep 11pm-7am ish) so I wasn't bothered by it; the neighborhood itself is quiet and I felt safe as a woman travelling alone with a dog. It is situated between the St. Roch and St. Jean Baptiste neighborhoods (about a 10-12 minute walk to each); I'd say 20-25 minute walk to the edge of Old Montreal.
I was nervous that I would not be able to contact Yan because of the initial automated messages, but Yan was extremely responsive to any inquiry I had and rushed over when I had an issue with the hot water. I get the impression that he really cares about this place and that made me feel even better about staying there. 100% would stay again.