I have talked to several folks who started out with portable mills that ended up adding planing and moulding to make high added value product. There are two problems, I dont think wood is planed green so its time to call up Nyle Kiln and buy a kiln and then have equipment to load it and unload it. The second problem is you need three phase power to run the equipment that is sized for reasonable thruput. One guy I talked to just got a surplus 3 phase generator and ran it when he needed it.I've been thinking very strongly about getting some sort of planer/moulder so I can make high value items from my rough lumber, but I don't even have a place to put a planer.
Funny on the poplar, I have bigtooth aspens on my lot and there is minimal demand for the wood locally. I just dropped 2 big ones and have 5 nice logs ranging from 24" diameter down to 16". I will haul them over to my friends bandsaw mill to get cut up into boards. Nice wood for interior but its rots quick when used outdoors unless its torrified.