Construction grade lumber, seems there's no bottom end to that market, and no way to insult the customer with a product too inferior. Fine hardwoods seem to be another matter. There's some with problems the vendors can't stand to sell or discard.
Go to a lumberyard that has an owner or manager. Find that person and ask them if they have any bundles they want to get rid of cheap. Possibly he'll give you a look of recognition. When I did that he had plenty. He sold me some bundles for what he paid minus a random factor. Some were "throw me a twenty".
So he forklifted his distressed bundles on my truck's lumber rack and bottomed my springs out a few times for a few twenties. He's a good businessman and maximizes inventory turns. He wants me gone quickly cuz his partners slept through that class.
For instance this bundle of ash with some beetles eating it. I don't care about the bugs because they'll die as soon as I seal the wood and cut off their air supply. Or I can freeze the wood and kill them that way.
Also a couple of bundles of "rustic" cherry for the cost of firewood. A customer had returned them for being too rustic (spits, knots, and rotted spots). But actually only the top layers were bad. So then I'm making container shelves from nice ash and cherry because it's cheaper than plywood. The materials themselves are so good these shelves will be bringing someone joy and materials for projects for many lifetimes after I'm gone.
Now that the lumberman knows I can make wood disappear, he's happy to give me more good deals. It's the start of a beautiful relationship.
P.s. Do you see any beetles in this photo? Only some of the boards had them...