Yesterday's article on plans for a new weekly newspaper incorrectly reported editor Jeff Stein's recent estimate of start-up costs for the project. The correct figure is $1.3 million.

If Washingtonians are ready by September, a new weekly newspaper will be ready for them.

Its editor and originator is journalist Jeff Stein, 39, formerly editor of the City Paper until his abrupt ouster in April. Since mid-May, Stein had been circulating a prospectus for "a thoughtful journal of local and national politics, arts and culture" among potential backers, including real-estate entrepreneur Mortimer Zuckerman, owner of The Atlantic, and Joan Bingham, a Georgetown investor with a longstanding interest in journalism.

Finally on Tuesday, Zuckerman and Bingham joined with Martin Peretz, editor-in-chief and president of The New Republic, in a three-way partnership to fund the venture at an undisclosed sum. Stein has estimated that it will cost approximately $300,000 to launch the project.

Although Stein is already hiring staff, the format, contents, title and design are still being decided, Peretz said yesterday. "We're going to do some market research" into advertiser and reader interest before issuing the prototype--an oversized tabloid of fewer than 50 pages--scheduled for late September.

Zuckerman, who said he was initially "somewhat skeptical" of the project, is now bullish. "The city's going to explode over the next decade," he said yesterday. "A critical mass is in place with that convention center," whose visitors he believes will "support the entertainment, retail and cultural life and bring in the suburban people."

The paper, he said, will "concentrate on the core areas of Capitol Hill, the West End, Georgetown and the transient residentials in hotels." However, "all this is still theoretical," he said, pending the outcome of "feasibility studies" now under way.

Bingham, whose former husband's family owns the Louisville Courier-Journal and Times, first met Stein "when he bumped into me about two months ago at a book party." She soon became enthusiastic about the project, and said yesterday that "I think I'm going to be the president. And I'm going to be the investor that's on the scene every day," helping to create a journal that "celebrates urban life" and is "humorous."

"Well, maybe not exactly humorous," Stein said yesterday. "Let's say a sense of irreverence or insouciance." The former Washington editor for The Progressive and contributor to magazines including Esquire, New York, Saturday Review and The Village Voice has not previously been conspicuous for insouciance. On April 16, he left as editor of the City Paper here after a bitter feud with its publishers over editorial control, later conceding that "I let everybody down by being too explosive."

As of Monday, he will operate out of temporary offices adjacent to The New Republic, whose publisher, James Glassman, is serving as interim overseer of the business until a publisher is found. But the paper "has no relation to The New Republic," Peretz said.

He also stressed that the new paper would in no way be an "alternative" or "underground" publication: "It's aimed at the active and interested part of the greater Washington population." And yesterday neither of Washington's two major alternative weeklies expressed alarm at the news.

"I'm not real worried," said Dave Wilson, managing editor of The Washington Tribune, some 40,000 copies of which are distributed free. If Stein "goes around paying people $350 or more for local stories, something's going to be amiss. But I don't think he'll have that kind of money. Besides, it's another market for writers--and that's what this town needs."

Russ Smith, editor of Baltimore's City Paper and copublisher of the Washington edition, which also claims 40,000 circulation, said "it won't affect us at all," since the City Paper is free and such papers traditionally survive more easily in the tough, conservative Washington market. "In fact, I'm surprised that Jeff, after his experience with us, would endorse a paid-paper concept," Smith said. "It would be very hard to make it work here. Look at what happened to Newsworks."

The ill-fated tabloid, calling itself "a hellraising alternative weekly," debuted in February of 1976 with a press run of 70,000 copies, a large staff (Stein was one of its writers), financing in excess of $250,000 and a cover price of 35 cents. After only 34 attractive and provocative issues, it ran out of money and ceased publication in October.

Nor are the new journal's investors worried about sharing the market with the free weeklies. "Any newspaper that sits on top of cigarette machines," Peretz said, "does not compete with any other paper that's sold."