Overall we had a pleasant stay (4 college students) and we had no hiccups with the host or their communication! They were in fact very lovely and welcoming to us, but some things you should know are that:
The apartment itself is a lot smaller than you would expect, but the fact that it is in the heart of Paris makes up for that and it is partly to be expected in the city.
To elaborate:
The couch bed, once extended, partially blocks the door, and the foldable table can't be placed when the couch is open. The sinks are rather small as well.
The appartment isn't really apt for hosting 4 people for these reasons but it is possible with a tight fit.