Before the house modeling project (had to give that away since I forgot to show you a few kinda important tools). here are some modifiers that allow you to add more
If you select 2 edges and hit the Connect tab, it will create new edges between the adjacent pair of selected edges. You can also specify the number of new edges, the amount of space between each other and their location.
This lets you subdivide edges and faces which basically means you create more vertices, edges and faces however you want. You'll see that the cursor changes to a plus sign when you're over an edge and if you click the second edge (which can be anywhere, you can cut across as many polygons as you want) a new edge appears.
We can now, finally, move to the next project!