We just finished our 5-day stay at Nicolas & Jean-Yves's home and I cannot recommend it more highly. The house (and, yes, it's a full house in the middle of Paris) is a true gem. All of the basic amenities functioned perfectly and the more luxurious ones (gym, sauna, etc.) were a terrific added bonus.
My wife and I were joined by 3 other couples and we all fit comfortably - each couple had plenty of privacy in their respective areas of the home. The common areas - especially the center courtyard - were perfect for hanging out and enjoying a drink or meal together as a group.
Nicolas and Jean-Yves were excellent hosts as well. Their friend met us promptly for key pickup upon our arrival and made sure everything was to our liking. Nicolas was extremely responsive during our stay if we had any questions.
The neighborhood was excellent too. It was far enough from the main tourist attractions to be quiet but with plenty of access to transportation to get around. There are a ton of bars and restaurants all around the area if you want to eat close to home too. We were there during the Euro Cup soccer tournament so the night life was super active and fun in the area.
I genuinely could not recommend a better place to stay for a group of friends or a family if you're looking for a real local experience and not just an overpriced hotel. It was truly an amazing experience for us and one we will never forget.