They are renowned for their business skills, and their main goal in life is to obtain wealth in any way possible. To die rich.
Ferengi 1: "I'm dying, please help me pay for a doctor's bill!"
Ferengi 2: "Heck no! Sixth rule of Acquisition; never allow family to stand in the way of profit!"
Ferengi 1: "BUT I'M YOUR CHILD!!"