Jonathan Segal’s message is clear: Keep it simple. Segal’s cut-the-middleman, screw-the-red-tape philosophy is straight out of Ayn Rand, and his fervor for urban infill development is flat-out evangelical. After a few minutes of listening to the 43-year-old architect/developer’s spiel, whole new vistas open up: You know that weed-choked lot across from your favorite coffeehouse? With a little imagination and elbow grease, it could be a gold mine.

Segal’s fiefdom is the formerly blighted section of downtown San Diego known as Little Italy (conveniently near the newly minted East Village). Since 1988, the native Californian has designed and built 245 smart, modern, and relatively eco-friendly rental units on odd and otherwise undesirable lots in and around the area, then turned them over to his wife Wendy to manage. “Control is everything,” says Segal about their landlord duties—and his aversion to private clients: “I’m making this wonderful widget. And when the day is done, I don’t want to give you the widget. I want to profit from it.”

As we tool around the neighborhood in Segal’s convertible, a beefy fellow developer in a big, black SUV leans out his window and shouts, only half-menacingly, “I thought we got rid of you!” as Segal smiles and waves. It’s an interesting turnabout. Segal was among the first to build here, when the area was all but abandoned by local land barons. Now that their soaring high-rises and Disneyfied condo blocks dwarf Segal’s airy lofts and two-story row houses, one of those same developers is buying him out—for a sum Segal would rather not publicize, but which is mighty enough to add “banker” to his list of roles. (All but a few of Segal’s rentals will be turned into condos. Control may be everything, but cash is king.)

Some call Segal the Tony Robbins of urban infill, but he’s more like a mini Donald Trump with a conscience. Segal’s units brim with money-saving and socially progressive ideas, in equal proportion: Grassy courtyards replace “stupid balconies.” His row houses are “convertible housing,” meaning their bottom floors can also be used as granny flats (one-bedroom, low-income rentals) or retail space—a nifty bit of social engineering that also guarantees tenant stability. In his Lusso Lofts, some street-level flats are used as Pilates studios or furniture workshops, creating the very environment that makes Segal’s other nearby buildings attractive to young urbanites. It’s a viral business model, and it works.

Segal ticks off a laundry list of money-saving, better-living elements of his urban designs: “Eliminate stair towers, eliminate elevators. The whole idea of underground parking is sacrilegious to us.” Case in point: Right next to one of Segal’s larger loft buildings is a similarly sized condo box by a rival developer. Whereas Segal’s tenants enter from the street into a sunny parking court lined with crushed gravel, their neighbors descend into a dank underground garage, a barred steel gate guarding its maw. “Think of the creepiest person you’ve met,” says Segal, “then imagine being stuck in a four-by-six-foot box with them. It’s called an elevator.”

Of course, Segal didn’t invent lofts, row houses, or infill—which is kind of the idea. He’s adamant that smart, simple housing can be built for a lot less than big, bad apartment blocks, which makes him more than a little frustrated. “Our stuff is less expensive than sucky architecture,” he fumes, “but you can’t mandate good design.” And what about the arcane zoning regulations, obstreperous NIMBYs, and bureaucratic molasses that usually cut progressive urban architecture off at the knees? Segal is appropriately vague when asked how he gets the copious variances and permits that allow his more interesting ideas to flourish; one suspects it’s a combination of architect’s charm and developer’s clout.

Segal also designs and builds his own home/offices, and sells them off when the next generation rolls around. His most recent—version 5.0—tackles the unique challenges of its site: the tony seaside community of La Jolla, just north of San Diego. In La Jolla, there’s no such thing as affordable housing and, one would think, no lot so undesirable that it fits Segal’s infill criteria. Yet in 2002, he found exactly that on the site of a former Shell gas station, a mucky, triangular brownfield that jutted into La Jolla’s most heavily trafficked intersection.

From busy Prospect Street, which funnels cars down to La Jolla’s shoppe-clogged main drag, Segal’s house—completed in June 2003 and dubbed the Prospect—is a blur. But as seen from the more neighborhoody south side, it’s an elegant modern presence in La Jolla’s clunky mix of Spanish-style mansions, block-long malls, and incongruous single-family bungalows.

“We tried to make some sense of the strange geometry,” says Segal of the isthmus, which he filled with rectangular stucco and Cor-ten steel volumes that utilize as much acreage as possible, without resorting to unusual (and expensive) custom shapes.

A series of bulwarks protects the living areas from street noise and looky-loos: First are the nine-foot outer walls. The city of San Diego wanted Segal to knock them down to the civic standard of three feet, but after some gentle arm-twisting, they agreed to accommodate the walls behind landscaping that reached the 36-inch limit. Though Segal finds even this regulation “stupid,” it turned out to be an improvement, as the sloping berm and drought-resistant plantings soften the building’s silhouette.

Behind the Prospect Street wall is a separate guest house, accessed from the main house by a path that leads past a narrow pool. The quarters are monklike in their privacy, and feature a tiny, high-walled outdoor courtyard that provides visitors a personal open-air space for meditation, yoga, or a furtive cigarette.

Segal installed the reflecting/lap pool as another sound barrier—the gurgling water cancels out traffic noise. The walkway past it feels like a drawbridge into the main house, an open, L-shaped volume of living/dining/kitchen sheathed in dark Sapelli wood panels—including the ceiling. “There’s no drywall,” notes Segal. “It’s all sup-posed to feel like one big cabinet.” The live-in humidor effect is softened by a shag rug in the living area and walls of thick glass on both sides that fill the room with light.

The lower level of the house includes a family room, with a projection TV and pool table. It also contains Segal’s former office space, a subterranean room with a tempered-glass ceiling that looks up to a sun-filled side yard. The former office is being transformed into a ’70s-style “love lounge,” complete with a wet bar.

The grassy yard on the quieter south side of the house leads to a perfectly square stand of pear trees near the lot’s narrowest point that, when fully grown, will provide a shady, Italianate canopy. On one stucco wall of the yard, Segal projects movies in the summer; on another is an outdoor gas fireplace of his own design. Segal’s nods to environmental responsibility include drought-tolerant landscaping, solar water heating for the pool, and photovoltaic cells on the roof.

Outside the master bedroom is a deck where you can enjoy the ocean view—if you can ignore the traffic noise. “I’m not a big view guy,” admits Segal. “But at night it’s great to sit up here and have martinis.”

Affixed to the prow of the Prospect is an abstract metal sculpture by Malcolm Leland, an 82-year-old artist who also worked with Los Angeles architectural icon Richard Neutra in the 1950s. To an Angeleno, the bauble is ironically reminiscent of the dingbat style of L.A. apartment buildings, those mid-century stucco boxes with names like Ultra Encino and the Galaxie that augment their sculptural titles with retro doodads, recalling overgrown Nelson clocks or metallic macramé.

But Segal doesn’t quite get the reference, and seems uncomfortable with it. He’s not about thumbing his nose at stuffy, old-money La Jolla, nor is his architectural practice ironic in the least. Segal enjoys the rewards of his success: a Porsche in his garage, a couple of motorcycles, armloads of awards for his contributions to the San Diego skyline. But what he craves most are architectural kudos. For all his business triumphs, Segal not so secretly wants to be considered an artist.

But there’s no Pritzker Prize for balancing a checkbook. Segal’s greatest gift to contemporary urban architecture is his empirical proof that smart design can be good for people—and even better for the bottom line.