I'd also like to recommend level 130+, just to be on the safe side. Especially when you encounter more than 1,2 monsters there, being able to use Ultimate Potions always comes in handy. Also, obviously, the more levels you get, the safer it is and the profit is much better.
I also like Deeper Banuta for the Serpent Spawn and Medusa since the corridors there are much more roomy and you have more space to run with the walls.