"I just live for 'Proud Mary,' " he says, his voice dripping with sarcasm. But he understands the song's popularity. "It's something they can sing, and they pay the bills." Occasionally, though, he refuses a request. "I draw the line at 'Joy to the World,' " says the 47-year-old Mr. Archer, referring to the 1971 Three Dog Night hit that has become a Happy Hour favorite. "I just say we don't know it."

His group -- ranging from a trio to a sextet depending on the event -- plays three or four times weekly on a lucrative circuit of weddings, birthdays, graduations, bar mitzvahs and, of course, conventions in the sunny coastal city. "The money is good, and most of the time the work is pleasant," says Mr. Archer.

It's also what he loves to do. "I have wanted to be a musician since the fourth grade," says Mr. Archer.

Still, there are moments when he has to swallow hard on the fact that working at one's first love may sound better than it really is. "A doctor told me the other night at a wedding, 'If I could play music professionally, I'd never have gone to medical school,' " Mr. Archer says. "I didn't tell him the truth: You're lucky you don't have to do something fun so much that it gets tedious."

It's just one of the dark little secrets more people are discovering as they make their passion or pastime a full-time vocation: Diversions, in large doses, can become drudgery.

"People are saying, 'If I'm ever going to try my hand at painting, or whatever, and get out of the 9-to-5 world, it's now,' " says Lynda Falkenstein, a small-business consultant in Portland, Ore. "But if you decide to follow your soul, to pursue the thing you think you were born for, then you could end up hating the very thing you used to love."

Why? For one thing, it isn't cheap. Making money off a hobby means spending more, too. The contest-winning amateur photographer who wants to go pro quickly learns that she might have to spend $20,000 to equip a studio from scratch.

Then there's the deflating criticism. "Doing embroidery for a friend is a lot different than for a customer," says Azriela Jaffe, who runs her small-business consulting service, Anchored Dreams, from home in Bausman, Pa. "When you're starting a business mainly to be independent and make money, and someone doesn't like, say, your widgets, you probably don't take it as a hit in the gut. But if they reject something from your heart, that hurts."

And the more emotion that small-business people invest, experts say, the less likely they are to develop a step-by-step business plan -- without which the endeavor may be doomed. "Too often the basic plan is, 'I feel that I can do this,' " says Larry Brockman, chief executive officer of the American Home Business Association in Salt Lake City. "Unless you're a computer hacker, what you feel about your new business idea may be worth very little."

Mr. Brockman says that people who are determined to jump into a new business because they think it will be fun are usually hard to reason with. "If it's something they're endeared to, they may have a problem and they won't listen," he says. "It just makes you want to slap them silly."

And there are some who get too close to their creations. Consider Kathy Hart, a 52-year-old, Paxton, Mass., bookkeeper-turned-silversmith specializing in Judaic art. Ms. Hart, who closed her bookkeeping business in 1997, has sold several necklaces, pendants and other items for up to $1,250. But her major effort, a seder plate that took 600 hours and five pounds of silver to create and was appraised at $80,000 -- remains unsold. Why? Says Mrs. Hart: "I couldn't possibly part with it."

How do people who turn their passions into professions navigate these challenges? Here's a look at three such people, the paths they followed and the lessons they've learned.

The Musician

David Archer has paid dues to play music.

This night, he is at Middleton Plantation, a restaurant housed in a restored Southern estate that's hosting Williams Technologies, a Charleston maker of automobile parts. "We always try to get David for our events," says Chris Emery, the company's director of sales. "He brings in good talent, and he's terrific at reading his audience." Tonight, Mr. Archer is accompanied by George Kenny, a retired high-school band director who's smooth on both the saxophone and flute, and by Charity Carpenter, a vocalist who also plays the tambourine.

Mr. Archer began in music by taking clarinet lessons in the fourth-grade band program of a Charleston-area elementary school. But by high school, he was devoting too much time to his passion, in the opinion of his parents, a contractor and homemaker. "They always wanted me to get a real job," he says.

His dad influenced him to enroll as a pre-dental student at Clemson University in 1969. "But I had to take organic chemistry, which was a course designed to weed you out, and that's what it did to me in pre-dentistry." So he switched to a major in psychology and a minor in fine arts, "which let me take all the music courses I could," and left him time to play in the school's Tiger Band marching group.

After graduation in 1973, he recalls "wandering into Fox Music, a family-owned music store" in Charleston.. He was hired to sell guitars: "A job in the back of the store for a guy with hair down to his shoulders. High-class people in ties sold pianos up front."

He worked there for most of the next 10 years, partly to support a night-time music-performing habit that didn't pay much. "I played in bars doing the one-man-band thing, covering James Taylor, Neil Young and Crosby, Stills & Nash songs," he recalls. "I made $50 a night, inhaled a lot of second-hand smoke and usually had to buy my own drinks."

Mr. Archer took a leave of absence from Fox Music for one year in 1982. "I was still single, turning 30 and having a midlife crisis. So I bought a plane ticket for St. Moritz and spent several months playing nightclubs there and skiing during the day. He also traveled through Scandinavia finding steady work singing at taverns. "It was fun, but I knew that life couldn't be forever, and exactly 365 days later, I flew home."

Buckling down at Fox Music, Mr. Archer cut his hair, donned a tie and moved to the front of the store to sell the business's biggest-ticket items: pianos. In dealing with the store's better-heeled patrons, he got an idea of how to improve his prospects in performing at night. "It suddenly dawned on me that you can play nice parties by putting on a tuxedo and focusing on standards that people usually request. I stopped pushing my favorite, jazz, which doesn't have mass appeal."

Mr. Archer also applied lessons in marketing from Fox Music by printing up brochures, polishing his sales patter and learning to bargain with customers. He began making his services known to managers of country clubs, yacht clubs and large hotels in the Charleston area. Thus his $50-a-night performances quickly became $500 gigs -- divided among members of the band he recruited. "By 1987, I was totally out of playing bars."

His popularity has led to an even more lucrative side of the music business: Booking performances for other acts. "I got so busy I was turning down dates, and customers would ask, 'Know another band I can get?' Now I represent about 100 bands, classical musicians and disc jockeys."

He quit selling pianos in 1997, "because my business performing and booking grew to the point where I didn't have time for the store."

But he's still sacrificing. "I work 75 hours a week, and there's no social life at all," he says. "I'm at parties a lot, but never my own."

Mr. Archer's wife, Paula, a veteran operating room nurse, quit that job in April to work full time as his administrative assistant. Now she handles her husband's musical emergencies. As he's setting up sound equipment for the Williams Technologies party, a cell-phone call warns him that the karaoke host he had booked for another event tonight has just been hospitalized. Mrs. Archer quickly tracks down another host and books him.

Meanwhile, Mr. Archer has learned a hard lesson about becoming a success at the thing he loves most. "I'm a professional musician, and I work with other musicians," he says. "But most of what I end up doing isn't actually music. Instead of singing, I probably spend more time talking to persuade some lady that my band won't ruin her daughter's wedding."

And being a professional musician hasn't necessarily made Mr. Archer a better one. "I always thought if I became a success in music I would practice more, write songs and explore the complexities of jazz. 
I haven't been able to do any of that."

Still, he says, "I'm a successful musician." And he estimates he has sung 
"Proud Mary" at least 2,000 times."

-- Mr. Johnson is a staff reporter in The Wall Street Journal's Orlando bureau.