I don't see how this is impossible, but if you are looking for quick gains, you will find frustration. otherwise, with a clean diet, good training, enough rest, and motivation, I can see this happening within a couple of months. I can't gain weight too quickly, me being 5'10.5 weighing in at 178lbs. I think I eat enough, but I know if I eat at least 1.5 times what I am eating right now, I could seriously gain some weight, as well as FAT.