James Dillard, owner of Dillard's Septic Service in Annapolis, Md., once rolled his company truck loaded with gray water from a dry well.

In the septic business, that's about the worst thing that can happen, a Houston-we've-got-a-problem moment. He was fortunate. The front of the truck wound up facing uphill in a drainage ditch so that the load drained out the back and not into the cab.

Dillard goes most days without getting a splash on his clothes. "The only odor you catch is when you take off the cap and agitate the solids," he says.

Dillard runs a business that most others consider beneath them. Dillard knows that, but he takes it to the bank. He understands the attitude. His father was in the septic business, and when James was in school, he was a little embarrassed of him. James tried other occupations, including managing a furniture store. But he has circled back to septic, where he charges $200 to $300 a visit. At about five stops a day, his annual income passes six figures with months to spare.

Turns out there are a lot of people doing well and getting rich running businesses large and small that others consider mundane, boring, beneath them or downright disgusting. Their success flies in the face of perhaps the most pervasive piece of career advice out there that goes something like this: Do something you enjoy, and the money will follow. Or, work at what you love, and you'll never feel like you work for a living.

When USA Today asked CEOs last spring what one piece of counsel they would give to their own graduating child, Dan Amos of Aflac, Brenda Barnes of Sara Lee and Dan Neary of Mutual of Omaha all said that if you pursue passion, treasure will follow.

The irony is that Amos and Neary sell insurance, and Barnes sells hot dogs and coffee cake. Warren Buffett became the nation's second-richest man investing in insurance and industries such as carpeting and roof trusses. Forbes magazine last month released its list of the 400 wealthiest people in the United States. It's peppered with those such as Herbert Kohler, worth $4 billion from plumbing fixtures. Wayne Hughes is worth $3.7 billion from self-storage; James Leprino, $2.1 billion from mozzarella cheese; Dean White, $1.7 billion from billboards; Christopher Goldsbury, $1.5 billion from salsa; Dennis Albaugh, $1.5 billion from pesticides, and Leandro Rizzuto, $1.4 billion from blow dryers.

Portable toilets are lucrative, so much so that they have a trade association called the Portable Sanitation Association International, which says the industry brings in $1.5 billion a year servicing 1.4 million portable restrooms worldwide with a fleet of 9,400 trucks. Most anyone can clean, but more and more don't want to, and so the commercial and residential cleaning services industry grew to $49 billion in 2005 from $29 billion in 1998, says John LaRosa, research director of Marketdata.

Thomas Stanley, author of the best-seller "The Millionaire Next Door," made a fortune himself by pointing out that the rich are often in mundane businesses and usually aren't the guys walking around in suits or at country clubs. They are scrap-metal dealers and dry cleaners, he says. They read trade journals such as Poultry Times and Water and Irrigation.

Fox's animated TV program "King of the Hill" saw humor in the contrarian road to riches. A 2006 episode called "Business Is Picking Up" has Hank Hill distressed because his son Bobby has an internship picking up dog droppings when he could be working for his dad selling propane.

When Bobby visits the home of his new boss, Peter Sterling, he finds him living in a mansion with an animated girlfriend more drop-dead gorgeous than Betty Rubble on her best day. Sterling gives Bobby this advice: "You don't get rich doing what you love. You get rich doing something no one else wants to do."

Jacob and Susan D'Aniello, both 30 and graduates of the University of Virginia, are finding this "King of the Hill" advice on the road to success is right on. In 2000, they started DoodyCalls, which polices yards for dog poop for about $15 a month. Susan thought nursing was her mission. But when the calls poured into her new husband's business, "I felt like I was missing out on so much."

Susan grew up in Great Falls, Va., where the median household income exceeds $170,000. It took two years before her mother told anyone that Susan dropped a nursing career for doody. DoodyCalls started franchising in 2004. It has expanded to 26 franchisees and will take in more than $2 million in revenue this year. That's only the beginning, Jacob says. There are plans for 275 franchises by 2011.

Forty percent of households have dogs. "They're all pooping. Nobody wants to pick it up. We're going to blow this out of the water," says Jacob, who was an information technology consultant before nature provided a fresh calling.