Michael K. Deaver, one of President Reagan's three top assistants, says he will leave the White House staff at the end of next year because he and his family cannot afford to live in Washington on his $60,662 annual salary.

The White House deputy chief of staff, who is considered closer to the Reagans than any other assistant, says he told the president at the outset that he intended to stay just two years and then return to private industry.

"I made a commitment to stay through the 1982 elections," Deaver acknowledged in a telephone interview yesterday. "After that, I'm going. I have no money left. We are living on our savings."

Deaver, who said he has made no secret of his plans to leave, said he "probably will go back into the business world in some form of public affairs" but that he has no specific plans or commitments. He said he will not rejoin the firm of his former business consultant partner, Peter Hannaford.

Together, they had formed the Deaver-Hannaford Co. after serving as top aides to then-governor Reagan. At the outset of the Reagan presidency, Hannaford chose to remain in private business and purchased the consulting company of Richard V. Allen, who became Reagan's national security adviser.

Officially, Deaver handles the president's scheduling and supervises the office of the military assistant to the president and the office of the First Lady.

But his importance and influence are far broader. He meets each morning with chief of staff James A. Baker III and counselor Edwin Meese III and the three also confer each morning with the president.

Deaver's advice is sought on all matters, ranging from policy to politics to personnel. And frequently, at the day's end, Deaver spends informal evening hours with the Reagans in their White House residence.

"It's been tough on Mike lately," said Sen. Paul Laxalt (R-Nev.), a friend of both Deaver and the president, in a report in yesterday's editions of the Detroit News. "He has been handling all of the personal, family things the Reagans want done as well as his other tasks.

"Of all the people who could leave, losing Mike will leave the biggest hole," the News quoted Laxalt as saying.

Deaver said yesterday that the cost of housing and the cost of living in the Washington area, and the cost of keeping two children in private school, have made it impossible for him to make ends meet on his $60,662-a-year salary.

Although he had lived on the West Coast before coming to the White House, the 43-year-old Deaver said he and his family liked living in the East and may decide to remain here.

Of all the president's top advisers, Deaver is considered to be the most protective of the Reagans. In the recent controversies involving Allen and Office of Management and Budget Director David A. Stockman, for example, he has reportedly taken the position that both should be replaced because their controversies brought unfavorable publicity to Reagan and his White House.