The law graduate was crowned the winner of the BBC Two series yesterday (October 16) over James Morton and Brendan Lynch.
Whaite is expected to earn around £500,000 by this time next year, according to The Sun.
A book deal has already been agreed, while the 23-year-old could "make it big" through TV and merchandise deals.
PR expert Max Clifford said: "If he takes the right advice, John could make half a million in the next year. If he doesn't build up a reputation in that time, he's lost his chance."
Speaking after his win, Whaite said: "I feel faint. I feel really queasy about it. It's not sinking in. I cannot believe it, I'm so happy."
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