Follow these instructions and you can make a money easy.
- Make 6+ Worm Food
- Have a Flail and Cobalt or Obsidian Shield
- Have full Molten Armor
- Have 200+ health
- Goto the Corruption
- Summon Eater of Worlds
- Hold Flail on ground (aim at legs, click and hold)
- Destroy Eater of Worlds without moving
- Collect money (+2000 copper, +100 silver each time)
- Repeat 6 to 9 until no Worm Food left
- Sell stacks of 99 Demonite Ore for ~8 gold.
When you destroy the head it drops the heart restoring 20 hp. More than it can damage you for.
Not to impress you or anything, but with 9 Worm Food I made over 1 Platinum in under 20 minutes.