We enjoyed staying in Ralf's apartment. He was welcoming and helpful at check in and the apartment was very comfortable. While it would not suit anyone with mobility problems the steep staircases and roof terrace were charming. Ralf had recently had some issues with damage - a hole in the door, for instance, and a broken window. I also felt a little bit vulnerable when I was on my own in the house as the internal doors are quite flimsy and the key is a master for the whole building.
It would have been easier to have two keys but it really wasn't an issue.
The location was perfect. We were able to walk everywhere. On the whole, a lovely experience in Amsterdam.