Answer by taking a quote from the following article:

Belushi's mother, Agnes Demetri (Samaras), was the daughter of Albanian immigrants, and his father, Adam Anastos Belushi, was an Albanian immigrant from Qyteze. Born in Humboldt Park, a neighborhood on the West Side of Chicago, Illinois, John was raised in Wheaton, a suburb west of Chicago, along with his three siblings: younger brothers Billy and Jim, and sister Marian. Belushi was raised in the Albanian Orthodox Church and attended Wheaton Community High School, where he met his future wife, Judith Jacklin. In 1965, Belushi formed a band, the Ravens, together with four fellow high school students (Dick Blasucci, Michael Blasucci, Tony Pavolonis and Phil Special).

In 1975 Chevy Chase and writer Michael O'Donoghue recommended Belushi to Lorne Michaels as a potential member for a television show Michaels was about to produce called Saturday Night a.k.a. Saturday Night Live (SNL). Michaels was initially undecided, as he was not sure if Belushi's physical humor would fit with what he was envisioning, but he changed his mind after giving Belushi an audition.  Over his four-year tenure at SNL, Belushi developed a series of successful characters, including the belligerent Samurai Futaba, Henry Kissinger, Ludwig van Beethoven, the Greek owner of the Olympia Cafe, Captain James T. Kirk, and a contributor of furious opinion pieces on Weekend Update, during which he coined his catchphrase, "But N-O-O-O-O-O-O-O-O-O!" With Aykroyd, Belushi created Jake and Elwood, the Blues Brothers. Originally intended to warm up the crowd before the show, the Blues Brothers were eventually featured as music guests. Belushi also reprised his Lemmings imitation of Joe Cocker. Cocker himself joined Belushi in 1976 to sing together Feeling Alright.  Like many of his SNL fellow cast members, Belushi began experimenting heavily with drugs to deal with the constant pressure. His unpredictable temper caused him to be fired (and immediately re-hired) by Michaels a number of times. In Rolling Stone's February 2015 appraisal of all 141 SNL cast members to that time, Belushi received the top ranking. "Belushi was the 'live' in Saturday Night Live," they wrote, "the one who made the show happen on the edge ... Nobody embodied the highs and lows of SNL like Belushi."

How long was he on Saturday Night Live?
Over his four-year tenure at SNL, Belushi developed a series of successful characters,