It's not an impossibility just an anomaly to be self-made and requires a lot more luck than just gumption and hard work. The far-greater majority of wealth is inherited. Technically you could argue El Chapo was self-made, so its possible but the less resources you have available the less probable. I recommend reading the book Capital in the Twenty-First Century by Piketty, it's an amazingly well researched and multidisciplinary work.