They are the people who plunge into one money-making venture after another, never quite hitting their stride until, at long last, inspiration strikes and everything falls into place. For Mr. Serros, 37, who today presides over Amber Diagnostics, an $8 million company in Orlando, Fla., it took years and goading from his wife before the light bulb came on.

The important thing is that the entrepreneurial urge to run his own show was in his bones. In high school, he started a landscaping business that quickly went from mowing neighborhood yards to maintaining commercial properties. At 21, he sold it for $50,000.

To pay his bills, he took a job at his father-in-law's plastic factory as an extruder, working his way up to sales, but all the while he was hatching business ventures. He traveled to the Dominican Republic in the early 1990's with a plan to import lobsters and sell them to seafood distributors in the United States. The venture fell apart before he made his first shipment because profit margins were too low and one of the men connecting him with people in the Dominican Republic was wanted by the F.B.I., he said.

Oriental rugs were next. He went to China and ordered enough rugs to fill two shipping containers. He had trouble selling them and had to pay to store them. That business also closed.

Then his wife, Nina, suggested that he try health care because it was growing quickly. So in late 1992, he called the Orlando Regional Medical Center and learned that it had a warehouse full of used bedpans, hospital beds and intravenous poles to sell. He bought the merchandise for $700, cleaned and repaired it and hit the road in his old pickup truck, stopping in towns and cities to seek buyers. One of his first clients was a group of brokers who sold baby incubators and bedpans to South America. "It was like horse trading," he said. "This was hard core."

The trips were grueling, especially given the low return he made on many of the items. Bedpans, for example, whether made of stainless steel or plastic, fetched about a quarter each. He had to sell hundreds in one shot to make it worthwhile. Hospital beds were more profitable - he could buy them for $50 and resell them for $125 - but not profitable enough. For all his time on the road and hard work, he was bringing in only about $50,000 a year in 1992 and 1993, running his business from an 800-square-foot warehouse and his home.

But at the end of 1993, he struck a deal that changed everything. On a trip to Miami, he made an unsuccessful sales call on a medical equipment dealer who turned the tables on him and talked him into buying two broken ultrasound machines for $500. "I didn't have money on me, so I had to get cash on my credit card from an A.T.M.,'' he said. He was still $20 short but the transaction went through. He brought the devices home, got one of them working by replacing a fuse and sold it for $2,500. It was his eureka moment.

"I said, 'Whoa,' '' he recalled. "I'd have to sell a lot of bedpans to make that kind of money."

For struggling small-business owners of all stripes, such a sudden realization that they have finally hit pay dirt is a common transforming experience, if only because persistence really does pay off. A lot of entrepreneurs are waiting for the "cataclysmic" event that tells them they are on to something, said Thomas K. McKnight, author of "Will It Fly? How To Know if Your New Business Idea Has Wings . . . Before You Take the Leap" (Financial Times, Prentice Hall 2004). "It will be like a dawn or a bloom," Mr. McKnight said. "You wake up one day and life will be a lot better. Customers will be calling you, asking you hard questions.''

In fact, Mr. Serros had stumbled on one of the fastest-growing niches in health care, said Scott Yen, a vice president who follows the medical equipment industry for Capstone Partners, a Boston investment bank. With insurance reimbursements declining, the medical equipment "aftermarket" is growing rapidly because health care institutions of all kinds are looking for additional revenue and ways to cut costs, Mr. Yen said. Hospitals can shed old equipment and smaller health care providers can buy revamped machines at bargain prices.

After his big sale, Mr. Serros began acting as a middleman between hospitals that had big-ticket used items like magnetic resonance imaging and mammography machines that they wanted to sell and brokers, private doctors, imaging centers and other parties who needed them. In 1994, Amber Diagnostics, named for his first daughter, had revenue of $150,000 - but Mr. Serros still had not realized its full potential.

But as word spread about his business and more brokers sought him out instead of the other way around, he became more focused. He hired someone to call hospitals and seek equipment and he bought a computer and a fax machine. In 1996, he moved into a 2,000-square-foot warehouse, created a Web site and started selling equipment directly to doctors and hospitals. This was a risky proposition because he had to deliver the goods and provide warranties. But it paid off, and in 1997, he made $1 million in revenue.

Even so, he still doubted his good fortune would continue and, just in case, he tried his hand at fixing and reselling old cars and even looked into real estate. "That's when my wife kind of dragged me by the ears and said: 'Stop coming down on yourself. You've got a good business going here,' '' he said. "And that's when it hit me - Amber Diagnostics is a real business."

He hired a service technician full time in 1998 to fix broken machines instead of subcontracting the work as he had done, and broadened his business outside Florida. Today, Amber is operating out of an 8,500-square-foot office and warehouse, has 24 employees and offers an array of services, including repairing and installing equipment on site for health care providers.

Mr. Serros plans to expand the company into about 25,000 square feet of additional space in December and to hire six people next year. He projects 2004 sales will increase to $12 million from $9.5 million this year. He sounds almost surprised at his own estimate. "I still ask myself, 'Is it real?' " he said.

It is - and his only regret is that he did not realize it earlier, he said. "I could have saved myself stress,'' he said. "I was waiting for the mother lode, but I came to the realization I was sitting on it."