Portable sawmills are the big thingy nowadays...............
We had one. They work pretty well, but lumber is rough fro it. Course one could have it planed down, but it’s extra cost. The mills are also a lot of work to maintain, a bit expensive if you have your blades done professionally. We always sharpened our own, (bought a blade sharpening rig for the mill), but it was time consuming.
In the long run though we saved a ton of money on the rough lumber we needed for barns and outbuildings, like sheds, storage buildings etc. And we didn’t mind the time it took to cut the ,umber, maintain the blades, the engine etc. Was kinda fun actually.