You can change the lot type, residential to community and vice-a-versa. In edit town click on the desired lot and then there is a button to change lot type. To make a brand new lot anywhere on the map, there is a world editor button. It is on the bottom left of the screen. From there you can choose what lot size you would like and place it where ever on the map, as long as it does not intersect roads, other lots, or placed on unchangeable terrain(forgot the exact wording from the game). If you can not find it, reply and I will log into my game to get a better description for you.