in practical use it's really not necessary, since a lot of those apartments are small enough in square footage to be well covered by one $80 5.x GHz capable 2x2 or 3x3 802.11ac AP. You can still get 400-700Mbps speeds through a 5 GHz channel, such as around 5150MHz, on any dual band equipment. Although 5 GHz goes through wood framed walls/floors a tiny bit, it doesn't go very far, to the point where you might see your neighbor's 5 GHz AP at a signal of -87.