It is 9 a.m., and Billy Carter is sitting in a bar in the Atlanta airport, nursing his fifth beer of the morning. "Pardon me, suh," stammers a young admirer. "Would ya mind letting me have that can when you're finished? Ah'd be right honored to have it."

Naturally, the First Brother is pleased to oblige. He may be something less than a prophet in his own hometown (he has twice run for mayor of Plains, Ga. and lost); his three-pack-a-day cigarette habit may leave the American Cancer Society fuming; and his celebrated beer guzzling may cause his fellow Southern Baptists to cringe. But Billy Carter has been kissed by celebrity.

The public yen for his presence is so strong, in fact, that the younger Carter brother is expected to earn a half-million dollars this year on the rubber-chicken circuit alone. He was paid $10,000 last month for appearing at a swamp buggy race in Naples, Fla., and Oakland A's owner Charlie Finley gave him $5,000 to throw out the first ball of the baseball season. Billy has already been approached to write his autobiography and to star in a network TV special and a movie. Endorsements are being negotiated with a brewery and a peanut butter producer, and he recently signed a hefty contract with Revell Inc., which will manufacture a Billy Carter toy pickup truck. It boggles the memory that only a few months ago he spoke to a travel agents' convention for nothing. "He made that commitment," says his Nashville agent, Tandy Rice, "before I entered the picture."

Though Billy isn't very picky about where he appears, he does steer shy of political fund-raisers—"If I said yes to one, I couldn't ever again say no"—and he prefers the frivolous to anything solemn. Thus, he turned down invitations to speak at Tulane Law School and the University of Georgia in favor of events like the Pole Climbing World Championship in Lexington, Tenn. and a baseball beer night in Cleveland.

On the road Billy is a curious blend of puckish good humor and down-home outrageousness. "I'm not the Carter who promised never to tell a lie," he assures his audiences. Then he amuses them with tales of Plains and his family. A question-and-answer session usually follows, and Billy is rarely at a loss for a zinger. "What do you think of Oakland?" he was asked on his visit there. "Well," replied Billy, wiping the beer suds from his mouth with the back of his hand, "it was the first place I saw after being in Korea for a year. I liked Korea better."

Sometimes such shooting-from-the-lip lands him in trouble. Recently Carter Gilmore, a black candidate for the Oakland city council, asked Billy jokingly if they were somehow related. "Well, if we are," observed Billy in the idiom, "someone left a nigger in the woodpile somewhere." Gilmore laughed but the next day demanded an apology. Irritated, Billy refused. "I meant it in good fun, period," he said. Later he mused with a grin, "I'll bet that one got Ham Jordan jumping up and down." (Hamilton Jordan is President Carter's top White House aide.)

Though Billy affects a what-me-worry insouciance, he is careful to avoid embarrassing either himself or the President. Loath to tarnish his image as a two-fisted drinker, he hardly ever turns down a beer but often discards it after one or two sips. "Wherever he goes, there's always someone who wants to cut a caper with him," says a friend. "They want to be able to tell their kids, 'I drank Billy Carter under the table.' Sooner or later, it will catch up with Billy because he has such a hard time saying no."

That's how it was in Oakland, where Billy agreed to attend a party for A's season ticketholders, then allowed club owner Finley to dragoon him into a night on the town. His famous grin fixed patiently in place, Billy pumped the hand of one total stranger after another as Finley tirelessly rounded them up. "Billy, I'd like to have you meet an old friend of mine," Finley would bellow. "What'd you say your name was, honey?"

Ordinarily, of course, Billy's arm doesn't have to be twisted. For if he is in some respects a closet sophisticate, he also craves simple excitement. Once, on a slow night in Nashville, he rushed his friends out into a corridor of the Hyatt Regency hotel to bet on the elevators as they came up from the lobby. Billy, who won $22,000 on his brother's election, dropped $60 on Hyatt's machinery. Though he doesn't mind losing, and has a tolerance for good ole boy banter, his normally placid temperament can erupt if he's made to look foolish. Last year he was tossed out of a bar after some drinking buddies jokingly told the bartender he was a homosexual and had been harassing them. Later in the evening he caught up with the group and slugged one of them on the jaw.

Unfazed by the occasional contretemps, Billy claims he finds more peace on the road than in Plains. "That town has gone to hell," he complains. If it has, of course, he has been acute enough to cash in on its ruin. Billy's two-pump gas station sells $8,000 a week in beer alone—"more than in the whole city of Americus," he says proudly. He recently organized a World Team Tennis match in Plains between the Phoenix Racquets and a team from the Soviet Union. Billy also owns a controlling interest in a local tour guide company, which earns about $175,000 a year but donates all profits to the town.

Though Billy delights in playing the redneck, he is jealous of his reputation for shrewdness. "Anyone who makes me out to be a farmer is just plain wrong," he says. "I may look like one, but I'm a businessman and always have been." Despite a 13-year age gap, the 40-year-old Billy is close to his older brother and has run the $2.8 million family peanut business almost single-handedly since Jimmy was elected to the Georgia legislature in 1963. "Jimmy calls me once or twice a week," he says. "Mostly we talk about Plains and family—I think he misses them up there in Washington. He never questions what I'm doing. He just trusts me."

The relationship, however, does not extend to the Internal Revenue Service, which demanded to see Billy's books for the peanut warehouse last winter, shortly after Jimmy's inauguration. Billy resisted at first, then grudgingly agreed to cooperate. But when IRS agents asked to see his personal bank records, he angrily drew the line. "It's none of their goddam business," he sputters. "They'll have to get a court order for that, and if they try I'll meet them on the courthouse steps with 300 reporters."

Although he is sought out constantly by the thousands of tourists who flock into Plains every day, Billy's schedule is virtually unchanged. He shows up for work at 6 a.m. to beat the celebrity hunters and leaves the office at 5 o'clock sharp. He rarely drinks during the day. but every month or so a plastic jug of moonshine is mysteriously delivered to the warehouse. "I don't know who brings this stuff in here," he says with a wink, "but I hear it's the best shine in Tennessee."

The Carter fame is not an unmixed blessing, and Billy's six children have found it confining. "We can't let them play in the yard," says his wife, Sybil. "You never know what those people will do. We had one guy who walked right onto our front porch and told us he wasn't going to move until he got to see Jimmy."

To escape the tour carriages, which roll by his white frame house every two minutes, Billy and Sybil had planned to build a new home on a remote corner of their farm. "Then a Yankee land developer said he was going to put up an amusement park—'Jimmy's Backyard'—right next to us," says Sybil. "The vision of busloads of people pointing fingers at us convinced us we should do something else." Last week the family moved into a 15-room house 19 miles northwest of Plains.

Because Billy is gone an average of two days each week, the day-to-day responsibility of running the warehouse has fallen to Sybil, who was only 16 when she married Billy 22 years ago. The wedding took place during her husband's first leave from the Marine Corps. "She's the glue holding the whole operation together—Billy included," says a friend. "There's not a thing that goes on in his life, or at the warehouse, that she isn't aware of. Billy kids her a lot, but he regards her as his very best friend—he doesn't hold anything back from her. She's as tough and shrewd as Rosalynn."

Lately Sybil, a soloist at the Plains Baptist Church on Sundays, has expressed concern about her husband's overpublicized drinking and his wheezing cough. But she has learned that to be married to Billy is not to reform him. "Billy has to be Billy," she says, "but he's a very bright man, a lot smarter than most people think. You won't find a man more devoted to his family anywhere. Besides," she adds with a knowing smile, "he doesn't like to be gone more than one night—and he always comes home."