Mark was born in Long Beach, California to Nick Sr. and Olga Sanchez. When Mark was four, his parents divorced; Mark and his brothers, Nick Jr. and Brandon, stayed with their father but their mother remained involved in their upbringing. Mark initially lived in Whittier and Pico Rivera; when he was six his father moved with the children to Rancho Santa Margarita, a predominantly white neighborhood of Orange County.
Mark's father remarried and raised them strictly, seeking to influence them to become leaders. Throughout his childhood and teenage years, Mark's father would have him combine athletic and mental training. Mark would have to dribble a basketball without looking at it while reciting multiplication tables; practice baseball swings in a batting cage while answering questions about the periodic table and similar combined drills that his father hoped would develop quick thinking and self-confidence that would guide Mark in all areas of life and not simply sports.
By the time Mark entered the eighth grade, he had developed an interest in football but was unsure of what position to play. His father consulted coaches Bill Cunerty, who formerly coached at Saddleback College, and Bob Johnson, the head coach at Mission Viejo High School. Both coaches stated Mark could be a quarterback if he applied himself and was open to learning the intricacies of the position. Nick Sr. trained Mark during sessions in their backyard or at the park. Mark, who was attending Santa Margarita High School, joined the football team. During his first pass attempt as a sophomore, Mark threw a 55-yard touchdown.
Prior to his junior year of high school, Mark transferred to Mission Viejo, where Johnson, who was recognized as a "quarterback guru", having trained professionals like Carson Palmer, was head coach. Under Johnson's tutelage, Mark felt he would have a better opportunity to become a better player. Johnson tutored Mark on the complexities of the position and in two seasons with the team, Mark led the Diablos to a 27–1 record culminating with the California Interscholastic Federation Division II championship in 2004.
Mark was named football player of the year by several major college recruiting services and was considered the top quarterback in the nation upon the conclusion of his high school football career in 2005. In July 2004, Mark announced his commitment to the University of Southern California.
While attending USC, Mark announced he had done something horrible. Mark caught his girlfriend cheating with his best friend. When he saw them together, he got so furious, he slit their throats with a machete. He buried the two bodies and his mom got scared and said,“You’re movin’ with your auntie and uncle in Bel-Air.” Mark whistled for a cab and when it came near the license plate said fresh and it had dice in the mirror. If anything Mark could say that this cab was rare but he thought,“Nah, forget it. Yo home to Bel-Air!” Mark pulled up to the house about 7 or 8 and he yelled to the cabby "Yo holmes, smell ya later" Looked at his kingdom he was finally there to sit on his throne as the prince of Bel-Air.