Ring of forging
Iron ore
Ghostspeak amulet if using Port Phasmatys' furnace
2 Ecto-tokens to enter Port Phasmatys unless Ghosts Ahoy is completed
10 coins to pay the Al Kharid guards unless Prince Ali Rescue is completed
Varrock armour
Smithing iron bars is profitable since demand is almost always present. Players can produce between 900 and 1,000 iron bars in an hour. That means the profit margin falls between and hourly.
Edgeville furnace is the closest furnace to a bank, and it has no requirements, but the others do. Neitiznot is the second closest, but it requires The Fremennik Isles. Port Phasmatys is third and requires two Ecto-tokens for entry unless the player has done Ghosts Ahoy. Lastly, players must pay 10 coins to pass through the Al Kharid gates to use that furnace if Prince Ali Rescue is not completed. An Amulet of glory or Ring of dueling can be used to bypass the entrance fee, however.