The cheapest way to get lumber is to buy rough lumber.
You’ll need a planer and jointer, but companies like Grizzly make an all in one unit well under a thousand — the 8” is around $600 or so. ...
With the price of lumber these days, being able to cut your own wood from the trees in your yard makes a lot more sense. So I built in inexpensive Sawmill with some 2x4's, a circular saw, and a ...