Billy Wagner has seen Southern hospitality virtually his whole life. The New York version of it blew him away.

Bowled over by the caring and commitment the Mets (and the city) showed to Wagner’s family, the self-described country boy finalized a four-year, $43 million contract with a fifth-year team option yesterday afternoon.

After he donned a blue cap and pulled on jersey No. 13, Wagner humbly expressed his thanks to the Mets for “taking a chance” on him. But this was no chance. The fireballing lefty closer is about as automatic as the sunrise.

“I guess it was something that was meant to happen to begin with,” said Wagner, 34, who made his major-league debut at Shea in 1995. “It seemed like all roads kind of lead to New York, as it’s turned out to be.”

It was the second press conference in as many days for the Mets, who welcomed first baseman Carlos Delgado to town Monday, and the second in nine days for Wagner.

After Mets officials visited Wagner’s Virginia farm on Nov. 2, he was whisked around the metropolitan area on Nov. 21 in a make-or-break visit with his wife, Sarah.

She was “a little nervous, and with all rights” about the Big Apple, Wagner said, but the wives of Tom Glavine and COO Jeff Wilpon took her to “The Phantom of the Opera” to cap a monumental day of house-shopping and clothes-shopping.

“I think New York opened up, and she really enjoyed it a lot more than I expected her to,” Wagner said. “And so did Madison Avenue.”

Wilpon said, “It didn’t matter what dollars you threw at him if his family wasn’t comfortable. He made that very clear at the beginning.”

GM Omar Minaya felt an instinct Sunday night that a deal could be completed quickly and, true to form, he hammered out an agreement. But again, the Mets needed to pay top dollar.

Wilpon and Minaya were concerned that if Wagner was still available at next week’s winter meetings, the Mets could miss their chance.

“We felt that a closer was priority No. 1,” Minaya said. “He is definitely for us, in our eyes, worth the contract.

“When you haven’t won for three years like we had before and you finish in last place, you have to give people a reason to come here.

“People are not going to come to New York for less money than other places.”

Wagner’s contract could be worth $50 million and take him through the 2010 season if an $8 million option is exercised. It was important the Mets gave a blanket no-trade clause and guaranteed the fourth year, because the Wagners are moving their three young children to the area.

Although Wagner praised Philadelphia’s new GM Pat Gillick, he panned his former team’s trade of Jim Thome to the White Sox and said it was going backward.

Wagner said he held no regrets about leaving Philadelphia after two seasons.

“I gave them every opportunity to sign me back,” said Wagner, who broke in with the Astros. “I gave them a three-year, $24 [million offer] at the trade deadline, and they kind of laughed at me.”

How good is the new Mets closer? In major-league history, nobody with more than 500 career innings has struck out more batters per nine innings than Wagner (11.99).

He’s converted 284 saves in 329 chances, an 86.3 percent rate. With 100 or more career saves, that puts Wagner behind Eric Gagne (96.4 percent), John Smoltz (91.7), Trevor Hoffman (89.5) and Mariano Rivera (87.9).

Wagner wants to win the World Series, and now thinks he has the best chance in his career to do that.

“I’m like everybody else: I expect great things,” he said.