It Almost Worked, but Lazy Filmmaking
Not a bad twist on the whole Welcome-to-Our-Strange Community...Stepford Wives...kinda genre, HOWEVER...
...the fact that there is never ANY indication as to the origins, purpose, perpetrators, etc. is complete bullshit. With the freedom of never having to explain anything, filmmakers can just put any weird events just to be weird. It's like going through a cheap haunted house ride at a low-budget carnival; just one chill after another. Then the ride's over. In this case, it's not chills so much as just frustrating events and obstacles.
I liked some of the fairly fresh takes on the genre, but felt cheated bigtime. I mentioned to my wife a few minutes in that I wondered if this was gonna be one of those movies that doesn't explain anything. It was. It didn't even HINT at an explanation.
And yes, as others have pointed out, we both both wondered why they didn't explore the other houses, but ultimately it wouldn't have mattered. They probably would've found themselves inside their own No. 9 unit anyway! Why? Who the hell knows? Or cares now.