Between the visit to the temple aged 12, and his baptism at the age of 30, we know very little about the life of Jesus. Consequently we also know little about the life of Mary in these years.
All we have is one verse:
And Jesus grew in wisdom, and stature, and in favour with men and God. (Luke 2:52)
This verse emphasizes again what was said earlier about the birth of Jesus being a real birth, and Mary being his real mother. If Jesus had existed before birth in heaven then he could not have "grown in wisdom", nor "grown in favour with God". Mary, who had "treasured in her heart" the incident at the temple must have had many occasions to wonder as her godly son grew into a godly young man.
During this period Mary would have been busy looking after her other younger children. Mary had at least four other sons; James, Joses, Simon, Judas, as well as daughters (Matthew 13:55-56, Mark 6:3). When he began to preach in Nazareth the people said aren’t all his sisters with us? (Matthew 13:56). This suggests that his sisters were still at home waiting to be married. Perhaps Jesus, as the older brother, even had to help provide for their weddings.
Mark tells us that Jesus, like Joseph, worked as a carpenter (Mark 6:3). This job was much as it is today, a skilled, but honest and hardworking trade. It would have given Jesus opportunity to meet all kinds of people and travel in Galilee. We know from historical records that when Jesus was in his teens, just starting his trade, the nearby town of Sepphoris underwent a major rebuilding which brought stonemasons and carpenters from all over the Roman empire. As it was less than an hour’s walk to Sepphoris it is almost certain that any young carpenter of Nazareth would also have spent some time working there. Sepphoris was a Greek-speaking town, and Jesus, who probably only spoke Aramaic (a form of Hebrew) at home, would have learned to speak Greek. The rebuilding of Sepphoris would also have provided extra income for his family.
A more important education in the life of Jesus is hinted at in the law of Moses which lays the following duty on all kings of the Jews.
When he takes the throne of his kingdom, he is to write for himself on a scroll a copy of this law, taken from that of the priests, who are Levites. It is to be with him and he is to read it all the days of his life so that he may learn to revere the Lord his God and follow carefully all the words of this law and these decrees, and not consider himself better than his brothers, and not turn from the law to the right or to the left. (Deuteronomy 17:18-20)
How many of us today would spend their time and money on making, by hand, a personal copy of the Bible? Yet according to the requirements of the law at some time before starting his preaching of the kingdom this is what the young Jesus did. Did Mary notice this and again treasure all these things in her heart? (Luke 2:51).
Jesus certainly "read it all the days of his life" because in the Gospels we find that Jesus quotes the Scriptures in almost every one of his sayings. His mind was full of the Scriptures.
Another insight into the life of the young Jesus comes in Psalm 22 (the famous psalm which prophesies in detail the crucifixion - see v.18). This is a Messianic psalm, where the Psalmist gets into the mind of Christ, saying:
Yet you (God) brought me out of the womb, you made me trust in you even at my mother’s breast. From birth I was cast upon you. From my mother’s womb you have been my God. (Psalm 22:9-10)
From the womb of Mary, even as a young child, Jesus trusted in his Father, and depended on him. In the same way we read of Jesus’ obedience to his Father:
During the days of Jesus’ life on earth he offered up prayers and petitions with loud cries to the one who could save him from death, and was heard because of his reverent submission. Although he was a son, he learned obedience from what he suffered. (Hebrews 5:7-8)
We can also conclude that at some time between the visit to the temple when Jesus was aged twelve, and the crucifixion, Mary’s husband, Joseph, had died. Jesus would never have asked John to look after his mother if Joseph was still alive (John19:25-27). Also, at some point before the start of his own work, his slightly older cousin John the Baptist became a great preacher (Luke 3:1-18). [Booklet by Steven Cox, Mary the Mother of Jesus, Section: The Unknown Years, access at: www.thisisyourbible.com/library/show/1035]
I hope you have found this helpful.