Answer by taking a quote from the following article:

Kidd was born in San Francisco, and raised in an upper middle class section of Oakland. His father, Steve, was African-American, and his mother, Anne, is Irish-American. As a youth, Kidd was highly scouted for AAU teams and tourneys, garnering various all-star and MVP awards. He attended the East Oakland Youth Development Center and frequented the city courts of Oakland, where he often found himself pitted against future NBA Hall of Famer Gary Payton.

Kidd was traded to the Phoenix Suns with Tony Dumas and Loren Meyer for Michael Finley, A. C. Green, and Sam Cassell during the 1996-97 season. In his first full season with the Suns in 1997-98, the team's win total improved by 16 games. The Suns, who finished the season with a 56-26 record, had been recognized for their fast-paced style of play with Kidd frequently leading a small lineup of four guards (Kidd, Kevin Johnson, Rex Chapman and Steve Nash) being on the floor at the same time together with Antonio McDyess playing at center.  In the 1998-99 season, Kidd averaged 10.8 assists per game to dethrone Washington's Rod Strickland as the league's assists leader. He also led the NBA with seven triple-doubles (the rest of the league had just 11) and was second in the NBA with 41.2 minutes per game (behind Allen Iverson's 41.5 mpg). Kidd averaged career highs in points (16.9 ppg), field goal percentage (.444), rebounds (6.8 rpg, best among NBA guards) and steals (2.28 spg, fourth in the NBA) and was the only player to be ranked among the top 50 in the NBA in 10 different statistical categories. The Suns won all seven of the games in which he had triple-doubles.  The Suns acquired Penny Hardaway from the Orlando Magic before the start of the 1999-00 season in hope of creating the best backcourt duo in the league. Combination of Kidd and Hardaway in the starting lineup was often labeled as the BackCourt 2000. Despite a decent 53-29 record, the Suns' season was spoiled by injuries to both of their superstars. Kidd, who broke his ankle late in the regular season, returned during the playoffs to help his team to beat the defending champion San Antonio Spurs and advance to the second round for the first time in his career.  The 2000-01 season was affected by Kidd's personal problems as he was charged with domestic abuse of his wife. The Suns, who struggled in the middle part of the season, finished strongly with a 15-6 record to secure another 50-win season. Kidd took on more of the offensive load after his teammates encouraged him to be more selfish. He recorded 30-plus points six times on the year and five times in the last 19 games. In one particular hot stretch, he scored 36, 32 and 31 in three consecutive games in mid-March, prior to which he had never recorded consecutive 30-point games.  During his stay in Phoenix, Kidd made the All-Star Game in 1998, 2000, and 2001 (in 1999 it was not held because of a lockout) and led the NBA in assists for three consecutive years (1999-2001). It was also with the Suns that Kidd rose to the status of the league's best playmaker as he was voted to the All-NBA First Team three years in a row (1999-2001). On June 28, 2001, after five seasons in Phoenix in which the team made the playoffs each year, he was traded, along with Chris Dudley, to the New Jersey Nets for Stephon Marbury, Johnny Newman, and Soumaila Samake.

When did he start playing for the Suns?
during the 1996-97 season.