Heather Finlay is making a $35 million bet that baby boomers are going to love living in the ultra-luxurious apartment complex her firm is building.

The upscale touches include gated entrances, fireplaces in master bedrooms, vaulted ceilings and glass chandeliers, skylights, dedicated telephone lines for computer hookups, separate showers and phone jacks in bathrooms, island counters in kitchens, private patios and private garages with automatic openers, a lagoon-style swimming pool (one of three pools) and a 10,000-square-foot social and business community center.The 32.5-acre spread provides room for tenants to grow vegetables and flowers in private gardens, "meditation" zones perfect for relaxing and picnicking and the de rigueur active areas for tennis courts and jogging trails.

Many apartment owners and developers already provide quite a few of those features, though generally not all together in a single property.

"This is something we hope will revolutionize the industry," said Finlay, a partner and vice president of JPI, one of the nation's largest apartment developers, based in Irving, Texas. If she's right, a new era of gilded apartment living is close by for homeowners who have had enough of shoveling snow and mowing lawns and for renters who want digs with even more comfort.

Baby boomers, who populated the "swinging singles" complexes of the '70s and the fitness-conscious apartments of the '80s, are the fastest-growing segment of the rental housing market in the '90s, a period shaping up as the "I-have-arrived" decade.

And what they want in their graying years, according to panelists at a seminar held here recently at the National Association of Home Builders convention, are larger, more luxurious and low-maintenance apartments.

Comfort living, like comfort food, however, must blend in the nostalgia as well as appointments of living in a house. That's what Finlay hopes to achieve with the construction of a 528-unit luxury complex in the Dallas suburb of Richardson.

The JPI apartments are larger than usual - up to 1,500 square feet, a unit for which a tenant could expect to pay a premium $1,300 a month. It's an affordable price tag for many, according to panelist Robert J. Sheehan, a suburban Washington, D.C., economist.

"Renters with incomes over $50,000 are the fastest-growing segment of the rental housing market," said Sheehan, principal of Regis J. Sheehan in Mclean, Va. The number of renters who picked up $50,000-plus paychecks increased by 1.1 million between 1989 and 1993, he said.

Part of the fatter paychecks is due to the general rise in income. But a major factor is that many baby boomers are moving into their peak earning years, according to Sheehan. It's a trend that increases the odds Finlay will nail her bet.

"The luxury rental housing market will continue to benefit from aging baby boomers who elect to remain renters for the next several years at least," Sheehan said.

He added this heads-up for apartment investors and developers: These tenants increasingly prefer townhouse-style units that offer downstairs-upstairs living.

In fact, townhouse rentals are downright hot. Sheehan said 700,000 townhouse units were added to the nation's rental housing stock between 1985 and 1993. While that's far fewer than the 1.4 million-unit increase in rental apartments, the percentage increase in townhouses was dramatic: Occupied town-house rentals rose by 39 percent in that period compared to 10 percent for rental apartments.

And the growth in townhouses is making the pejorative description "apartment-size" a misnomer. In 1986, at the end of the last multifamily construction boom, the average size of an apartment was 876 square feet, Sheehan said. By the end of 1994, it was 1,015 square feet - with luxury developers bumping up the living space even more.