You can get one really early, without going to Blight Town or buying one from the blacksmith. Just need to hang around and kill the demon at the end of the tutorial then loot his corpse. Be careful though, once the Mindflayer is done with the demon, he will declare you are useless and try to kill you. Make sure to have your character hanging out at the switch, use the githyanki or Us to send the sword to your inventory.
