I've got a 3x3 space covered in paths. There is many like it all in a row with two-space inbetweens. I know there can be a rock on the side of a house, but...
Infront of that 3x3 square is a rock. Will a Villager move there?
A villager's house can occupy the top row of X's with the entrance space occupying the X in the center of the square. You could also have a house with the lower-right corner of the house on the center of the square and its entrance space being on the lower-left X.
If it's there, they won't move in. If it's an ore rock, you can break it and it'll just respawn elsewhere. Unfortunately, if it's a stationary rock, then you won't be able to get anyone to move into that exact spot :\