Ascend to the roof of the high-rise building for the elderly in Villa Victoria--the 815 units of housing built and run by a grassroots Puerto Rican organization in Boston's South End neighborhood--and an astounding view awaits you.

Immediately below are the Hispanic plaza and distinctive pitched roofs, the bright yellow, orange and brown earth colors of the town houses of Villa Victoria--proof positive that a housing "project" doesn't need to look like one. Glance just a bit farther to the surrounding South End streets and you see roof gardens and stylish rooftop cupolas sprouting left and right. "Gentrification" is overtaking virtually every street of a once desperately poor neighborhood of some 40 ethnic backgrounds.

A few blocks to the north in Boston's famed Back Bay stand the glass-sheathed John Hancock tower and the new buildings of Copley Place, a multi-million-dollar retail-office-hotel project just built over freeway air space. All across downtown Boston, new buildings have risen or are in construction. Even in South Boston--a low-income, fiercely parochial Irish enclave cut off from the rest of the city by railroad tracks and an expressway--a $300 million waterfront development has been proposed.

My guide was Jorge Hernandez, executive director of Inquilinos Boricuas en Accion (IBA), Puerto Rican Tenants in Action, Villa Victoria's founder and operator. He was quick to note that the development and gentrification sweeping across Boston do not assure a better life for all. High levels of unemployment afflict the people of Villa Victoria and all poor Bostonians--Hispanic, black or Anglo. Low-income housing is in short supply. When Villa Victoria took applications for its last section two years ago, there was a near riot as 5,000 desperate people came clamoring to apply for 190 units.

Not many cities are as far down the gentrification-no-room-for-the-poor path as Boston. But more and more are getting there, and Hernandez raises a timely, vital warning. Steps must be taken to secure a decent supply of low-income housing before it's too late, he said.

The problem is made more urgent by the fact that federal contracts to subsidize thousands of low-income rental units are running out. There's real danger that speculators may gain control of the nonprofit boards that sponsored the housing. Alternatively, when the Department of Housing and Urban Development gets title to the properties, it may auction them off to the highest bidders. Either way, hapless tenants may find themselves out in the cold.

If there's an outstanding model of how to save housing for the poor, and create more, IBA and its Villa Victoria are it. Born out of Puerto Rican neighborhood opposition to a bulldozing urban-renewal scheme of the 1960s, the project prevailed against initial opposition in the Boston Redevelopment Authority, hostile lawsuits by real-estate interests, and even arson attacks.

The secret lay in thorough and sometimes inspired grassroots leadership, painstaking research, imaginative design involving neighborhood people, and a touch of clever politics. Increasing local Puerto Rican voter registration by some 75 percent won the crucial support of Mayor Kevin H. White.

IBA not only became the city-sponsored developer of Villa Victoria but decided to act as the rental manager--marking as one observer noted. "the real centralization of power over space by the Puerto Rican community," as one observer noted. The sense of territoriality is overwhelming when one walks across the heavily used central plaza, with its bright Puerto Rican mural, and then strolls through the new looped streets, laid out to discourage automobile traffic and encourage front-step socialization.

Villa Victoria has its share of problems. Half the population is under 19, and some wear and tear shows, along with ample litter and stretches of dead grass. The project has a growing middle class, but many residents are minimally educated and unskilled. Some 60 percent receive public assistance. The organization finds it necessary to be a tough landlord. "If your rent is 10 days late, you get 14 days notice--or have a very good reason," says said Hernandez. Ten or 12 evictions are ordered annually--but few families want to risk losing such prized housing.

Making all this operate smoothly is a job far more complex than most real-estate managers ever dreamed of. IBA today is a $5-million-a-year business, employing 85 people persons. It is financed by no less than 30 separate funding sources, ranging from government contracts to foundation and corporate gifts.

The organization has a full staff engaged in social services--crisis intervention, family and senior-citizen counseling, recreation. It seems to lack only its own citywide employment placement service for job-hungry youth. It sponsors several festivals a year; it runs a full musical program; it's set up to do cable television transmission; it sponsors a community credit union with 500 members and some $400,000 in assets. Moving into commercialization, it has a laundromat and several new facilities, including a restaurant, about to open.

It's the complexity of those operations, and the need for tough, sophisticated leadership as conversant with politics as it is with business that makes one wonder whether the network of community-based organizations operating across the country today is sufficient to cope with mounting problems involving low-income housing problems.

There's no easy answer to that question, even though a growing coterie of highly competent housing groups--many aided by grants and loans from the New York-based Local Initiatives Support Corporation--can be found operating in numerous U.S. cities. IBA would like to help by acting as an adviser to neighborhood Hispanic groups in particular.

What's certain is that, if grassroots housing groups can't move rapidly to do the job, thousands of low-income people will be thrown onto the streets each year. And their eviction will come just when they're needed the most to assure healthy, mixed neighborhoods in our reviving cities.