J&B Builders started out with $10,000 and a Capitol Hill town house three and a half years ago, but this month the development firm is putting the finishing touches on a $5 million luxury condominium office complex in Bethesda.

J&B are Bob Jersky and Joann Kay-Jersky, a young husband and wife developer team that has managed to build success upon success in a few short years during one of the worst periods in the construction industry's recent history.

"It would have been almost impossible for us to start out with a million-dollar project," Jersky, 32, said earlier this week. "We were like any developer starting out. We had a lot of mistakes to make, a lot of ideas to test. It is a difficult business."

The Jerskys are like many successful young developers who have entered the multi-billion-dollar industry. They started with renovating one row house on Capitol Hill into two condominiums and built up their expertise project by project.

"There is no such thing as a school for developers," said Kay-Jersky, 26, a native Washingtonian whose family has been in the construction business since 1947, most recently as Kay Brothers Builders of Laurel. "I never made a conscious decision to be a developer. It was just tackling one project at a time and feeling like I could just tackle anything."

The Jersky's latest project is the Old Georgetown Office Park, 31,000 square feet of luxury town houses in Bethesda's Battery Park, which will be sold this fall. Jersky and Montgomery County planning officials said most neighboring residents of the office complex approve of its low-key residential look, designed by architect Elliott Gitlin.

The Jerskys say several doctors and an accountant already are interested in buying units in the $5 million complex.

"There is this idea that developers are all these wealthy older men with a lot of money to throw around," Jersky said. "But many developers are like us--smaller and willing to work with the community so things go smoother."

Both Jersky and Kay-Jersky worked for Holland & Lyons, a Washington-based development group, before striking out on their own four years ago. They say their time at Holland & Lyons was almost like an apprenticeship. They learned about the development business without taking risks.

"We were there when the construction market was booming," Jersky said. "You could build anything, and it would sell, sell, sell. We struck off on our own at the worst possible time: right when the market was falling."

Kay-Jersky said, however, that the poor market made them better developers because they had to have good projects to sell them. "We really learned to find out what people want," she said.

The poor market also gave them a chance to check out their intuition. "In this business, you have to go with gut feelings," she said. "If it's not there, then it's not going to work."

Their first project, the Capitol Hill row house near Union Station, sold for $130,000, and the couple--who were married two years ago--turned to several projects in Logan Circle. They built a four-unit condominium, law offices and a residential-commercial complex within two years.

"We were able to have more than one project going at once," he said. "The market was awful, so we were careful. But we had a good feeling about the projects we were doing. They were good ideas, and we were doing them right."

From Logan Circle, the Jerskys turned to the Old Georgetown Office Park.

Jersky said he realized the office complex site had been the center of a bitter fight between neighbors and another developer who proposed to build an office building.

"It was obvious the neighbors were a force and that they did not want an office building," Jersky said.

"We met with them right off to get their ideas on a town house office complex in keeping with their neighborhood. We kept consulting them all the way through the planning."

The Jerskys maintain they never would have been able to tackle the Old Georgetown project without the help of their partner in the venture, J. G. Georgelas and Sons, and the advice of other, more experienced developers.

"Lawyers, contractors . . . they were all ready with advice and ideas," Kay-Jersky said. "Yes, this is a competitive business, but people were wonderful."

She said the bad market of recent years forced many small developers to quit the business, leaving the field to big-time developers who had enough money to hold on to their projects and to smaller developers, such as J&B, that perservered with luck and good projects.

The Jerskys have another, as yet unannounced, project in the works and ideas for the future.

"I don't put a limit on anything we can do," Kay-Jersky said. "I'm flexible. I'm willing to look at commercial and housing."

"I think we still have a lot to learn," her husband said. "We've been pacing ourselves. There are no overnight successes in this business--just hard work and good people." CAPTION: Picture, Developers Joann Kay-Jersky and Bob Jersky at their $5 million condominium office complex in Bethesda's Battery Park. By Barbara Hansen-The Washington Post