It's not easy, such profit is usually made with high-risk operations, like trading/holding altcoins.
Best way to tranform 2 btc into 4 is to put everything on primedice xD
You'll have nearly 50%chance to win what you want!
thats true, i think it is also the best way to double your money, in my opinion other methods will just waste your money and give you no benefits most probably