Once you have chosen to do this you will be dealt a third card and no more. Your hand will only consist of the 3 cards. You would now be playing 2 separate hands, each starting with one of the two split cards. You will now be dealt a second card to one of the hands. After this hand is played out the second hand will be dealt a second card and continued until that hand is played out.
All regular rules apply to each hand with the ability to double down.
You may only split your hand once and a new wager equal to the initial wager will be placed for each split hand. When splitting aces, the player will only receive one card on each hand. When the dealer's exposed card is an ace, the player will be given the option to place an insurance wager. This wager will equal one half of the original bet and will be placed on the insurance line. If the dealer has blackjack the player will get paid 2 to 1 on the insurance bet with the original bet being lost.