It's only a small piece of land in Harvard Square, but there are those who think it can be used to accomplish a world of good.

When the Archdiocese of Boston announced that it would accept bids later this year from real estate developers seeking to build on what is now a parking lot for St. Paul's Church, people started thinking. Some thought it would be a good idea to build a fancy hotel or luxury condominiums on the DeWolfe St. site. Others thought the property would be a suitable site for Harvard graduate student housing.

Still others thought it would make sense to build an experimental community project on the property, sandwiched between Leverett and Quincy Houses, that could unite people of differing backgrounds and diverse incomes under one roof.

One of those quixotic Cantabrigians is Jana Kiely, co-master of Adams House and a woman who thinks the plot of land close to the river's edge can be put to more noble use than profit-making.

"Just take one drive through this city and you'll see how important such a project would be," Kiely says. "We need to convince people that you don't take care of social problems by sticking people below a certain income into some ghetto.

"Look at how people suffer from the lack of community in our society. What we have are islands of people with the same income, breeding the distrust that makes for violence and that makes for greed."

To help combat this social ill, Kiely and a group of Cambridge and University activists envision constructing "a model type of community" in which homeless and low-income families would live and interact with moderate-income Cambridge families and Harvard affiliates. But the plan for an experiment in "totally income-integrated" living has run up against a familiar stumbling block that has fallen in the path of many similar idealistic projects before it: money, or the lack thereof.

While such a project would be expensive to build and costly to operate, professional realtors say it undoubtedly would not be a moneymaker. Housing for transients and low-income families cannot compete with the posh condos and fancy boutiques which pay Harvard Square's top price of $60 per sq. ft. in rental fees.

Further complicating the plan is the Archdiocese's desire to use the valuable land--the most valuable undeveloped property left in the Square--as a source of income to rebuild its crumbling Boys Choir School and the Harvard-Radcliffe Catholic Student Center on the north side of Mt. Auburn St. As a result, any financing scheme for the Kiely project has to take into account not only operating and construction expenses, but also the church's desire to get top dollar for its property lease.

To find out just how much money is needed to implement this innovative proposal, the Kiely group approached the Harvard Planning Office and asked it to estimate how much a mixed-income project on that site would cost.

"We listened to them describe what they thought ought to happen on the site," says Robert A. Silverman, director of the Planning Office located high atop Holyoke Center. "We developed hypothetical numbers for them, what their concept would amount to in bricks and dollars."

But the results of what Silverman calls his "academic excercise" were not that encouraging. According to Harvard's computations, the Kiely plan, after financing and operating costs were added up, would lose nearly $600,000 annually.

One participant in a meeting of the activists last January paraphrased a popular comedian to describe the gap between the group's desires and its resources. "You can be millionaire, and never pay taxes," the local activist said. "First, get a million dollars..."

Enter Harvard

One place it made sense to look for such a great sum of money was the University, which owns 25 percent of the land in Harvard Square and is already the largest property-owner in Cambridge. Last month Kiely met with President Derek C. Bok to convince him that the University should help underwrite the public-private housing complex. "I tried to show him the educational advantages of the project and why it would be good for Harvard and the community," she says.