Dunno if this would work for your situation BUT you could just place like target points manually on your map where you would like to spawn houses and then at run-time get all target points, and have a function that loops through a random number of times to a random index in the array of points and pulls out the location of the target point and spawns a house at that location. It would be more manual work placing the points but you could ensure that you would have the room for a house at each position and it saves you from the complexity of traces and such to determine an appropriate location.