MIDDLETOWN, NJ - Is Jon Bon Jovi the latest New Jersey millionaire to flee to Florida? Reports are in that the rocker bought a five-bedroom oceanfront villa in Palm Beach for $10 million last March. And now his 18,000-square-foot Middletown mansion is up for sale. The price is only available "by request," and you can bet the realtor won't consider us a serious buyer for the 15-acre estate gloriously perched on the Navesink River. You can't blame Bon Jovi for heading south; it was reported the Middletown estate carried $281,477 in property taxes last year. And the property taxes on the 6,000-square-foot home in Florida? Just $46,466 last year, plus no state income tax for full-fledged residents. Any shrewd kid from Sayreville can do the math on this one.