What does Nixon do for the rest of his life after he resigns as the President?

After assuming the presidency when Nixon tendered his resignation, President Gerald Ford pardoned Richard Nixon for all the crimes committed from the Watergate scandal. Advisers to Nixon counseled Nixon to accept the pardon. Nixon was reluctant to accept the pardon preferring to challenge the crimes against him in court. He believed by not challenging the crimes in court he was admitting to being guilty. After consulting with friends and advisers, Nixon chose the wiser course of action by allowing the pardon to stand and in President Ford's words, "Our long national nightmare is over."
Post-presidential life can be a difficult adjustment for any president. Most join corporate boards, start international foundations, retire, or try to remain relevant by making appearances at various events. These opportunities would not be available to Nixon as his image was tainted by scandal and his public persona discredited if not thoroughly disliked by the public. Returning to California with his wife Pat, Nixon was a broken man with little or no future in the public eye and few prospects as a private citizen. These surely must have been dark days for the politician who had come back many times from what for others would have been total political defeat.
In deep debt from repaying lawyers, Nixon turned to the only resource available for him to regain his financial footing, writing an autobiographical account of his life. Though unpopular as a public figure, Nixon's book would generate significant interest from scholars as well as the public, and reportedly earned him two-million dollars. The book also created opportunities to appear on television, and many still watch clips from his interview with David Frost, one of the most popular interviewers on British and American television. The public appearance earned Nixon reportedly $600,000 and though met with some skepticism, put Nixon back into the public spotlight. He also authored several other commercially profitable books which generated new opportunities for Nixon to appear publicly without the public rancor he earlier caused.
One of the achievements of the Nixon administration was the opening of relations with China. After making a few tentative low-key public appearances, Nixon traveled to China. While in China he was warmly received and again generated some amount of positive press for himself. The road to rehabilitating his image and public persona had begun. Nixon moved from his native California to New York, where he started being seen in small private gatherings.
Not shy about offering advice, the next three presidents privately consulted with Nixon about how to proceed with relations with the Chinese. The United States policy regarding China bears the fingerprints of the former president, and though not considered to be an expert in domestic policy, Nixon was able to generate favorable press and favorable comments as an adviser on foreign policy issues. Former presidents are a select and limited private club. Mostly kept secret from the public is how often former presidents advise and talk with the current occupier in the office. Nixon was able to use this channel to continue to rehabilitate his personal image and remain relevant in United States politics.
Some historians point to the 1986 Newsweek cover story proclaiming Nixon was back as the point at which Nixon regained a favorable standing with the American public. Time certainly was more kind to the disgraced president than perhaps he was to himself. Nixon died on April 22, 1994. His funeral was attended by dignitaries from around the world. As is the tradition for most presidents when they pass away, the current president provides the eulogy. President Clinton spoke to Nixon's imprint and success in foreign policy. Ironically, the First Lady Hillary Clinton had served as an attorney on the Watergate Committee investigating Nixon for his role in the Watergate crimes. It seems Nixon had come full circle and at his death could claim a certain amount of personal vindication.
https://millercenter.org/president/nixon/life-after-the-presidency

https://www.theatlantic.com/politics/archive/2014/08/nixons-resignation-40-years-later/375447/