Answer the question at the end by quoting:

Cary Grant (born Archibald Alec Leach; January 18, 1904 - November 29, 1986) was an English-American actor, known as one of classic Hollywood's definitive leading men. He began a career in Hollywood in the early 1930s, and became known for his transatlantic accent, debonair demeanor, and light-hearted approach to acting and sense of comic timing. He became an American citizen in 1942. Born in Horfield, Bristol, Grant became attracted to theatre at a young age, and began performing with a troupe known as "The Penders" from the age of six.
Stirling refers to Grant as "one of the shrewdest businessmen ever to operate in Hollywood". His long-term friendship with Howard Hughes from the 1930s onward saw him invited into the most glamorous circles in Hollywood and their lavish parties. Biographers Morecambe and Stirling state that Hughes played a major role in the development of Grant's business interests, so that by 1939, he was "already an astute operator with various commercial interests". Scott also played a role, encouraging Grant to invest his money in shares, making him a wealthy man by the end of the 1930s. In the 1940s, Grant and Barbara Hutton invested heavily in real estate development in Acapulco at a time when it was little more than a fishing village, and teamed with Richard Widmark, Roy Rogers, and Red Skelton to buy a hotel there. Behind his business interests was a particularly intelligent mind, to the point that his friend David Niven once said: "Before computers went into general release, Cary had one in his brain". Film critic David Thomson believes that Grant's intelligence came across on screen, and stated that "no one else looked so good and so intelligent at the same time". After Grant retired from the screen, he became more active in business. He accepted a position on the board of directors at Faberge. This position was not honorary, as some had assumed; Grant regularly attended meetings and travelled internationally to support them. His pay was modest in comparison to the millions of his film career, a salary of a reported $15,000 a year. Such was Grant's influence on the company that George Barrie once claimed that Grant had played a role in the growth of the firm to annual revenues of about $50 million in 1968, a growth of nearly 80% since the inaugural year in 1964. The position also permitted use of a private plane, which Grant could use to fly to see his daughter wherever her mother, Dyan Cannon, was working. In 1975, Grant was an appointed director of MGM. In 1980, he sat on the board of MGM Films and MGM Grand Hotels following the division of the parent company. He played an active role in the promotion of MGM Grand Hotel in Las Vegas when opened in 1973, and he continued to promote the city throughout the 1970s. When Allan Warren met Grant for a photo shoot that year he noticed how tired Grant looked, and his "slightly melancholic air". Grant later joined the boards of Hollywood Park, the Academy of Magical Arts (The Magic Castle, Hollywood, California), and Western Airlines (acquired by Delta Air Lines in 1987).

What is the Grants business interest about?

real estate development in Acapulco

Answer the question at the end by quoting:

David Michael Letterman (born April 12, 1947) is an American television host, comedian, writer, and producer. He hosted a late night television talk show for 33 years, beginning with the February 1, 1982, debut of Late Night with David Letterman on NBC, and ending with the May 20, 2015, broadcast of Late Show with David Letterman on CBS. In total, Letterman hosted 6,028 episodes of Late Night and Late Show, surpassing friend and mentor Johnny Carson as the longest-serving late night talk show host in American television history. In 1996 Letterman was ranked 45th on TV Guide's 50 Greatest TV Stars of All Time.
In 1975, encouraged by his then-wife Michelle and several of his Sigma Chi fraternity brothers, Letterman moved to Los Angeles, with hope of becoming a comedy writer. He and Michelle packed their belongings in his pickup truck and headed west. As of 2012, he still owned the truck. In Los Angeles, he began performing comedy at The Comedy Store. Jimmie Walker saw him on stage; with an endorsement from George Miller, Letterman joined a group of comedians whom Walker hired to write jokes for his stand-up act, a group that at various times would also include Jay Leno, Paul Mooney, Robert Schimmel, Richard Jeni, Louie Anderson, Elayne Boosler, Byron Allen, Jack Handey, and Steve Oedekerk. By the summer of 1977, Letterman was a writer and regular on the six-week summer series The Starland Vocal Band Show, broadcast on CBS. He hosted a 1977 pilot for a game show entitled The Riddlers (that was never picked up), and co-starred in the Barry Levinson-produced comedy special Peeping Times that aired in January 1978. Later that year, Letterman was a cast member on Mary Tyler Moore's variety show, Mary. Letterman made a guest appearance on Mork & Mindy (as a parody of EST leader Werner Erhard) and appearances on game shows such as The $20,000 Pyramid, The Gong Show, Hollywood Squares, Password Plus and Liar's Club, as well as the Canadian cooking show Celebrity Cooks (November 1977), talk shows such as 90 Minutes Live (February 24 and April 14, 1978), and The Mike Douglas Show (April 3, 1979 and February 7, 1980). He was also screen tested for the lead role in the 1980 film Airplane!, a role that eventually went to Robert Hays. His dry, sarcastic humor caught the attention of scouts for The Tonight Show Starring Johnny Carson, and Letterman was soon a regular guest on the show. Letterman became a favorite of Carson and was a regular guest host for the show beginning in 1978. Letterman credits Carson as the person who influenced his career the most.

Was he successful from the start?
By the summer of 1977, Letterman was a writer and regular on the six-week summer series The Starland Vocal Band Show, broadcast on CBS.