Many theories have been offered, but these have been based on his plays, not on historical evidence. It has been suggested that he had legal training or military experience, because his plays show such deep understanding of both professions. One theory was that he worked as a schoolmaster There was even a legend that he had been arrested for deer –poaching in his youth.
However – apart from some evidence that his acting career may have begun before 1592 – the "lost years" remain lost.
After the christening of his twins in 1585, he 'disappears', for 7 years.
Eventually, he turns up in London, apparently as a writer of plays for the
'Rose', theatre on Bankside.
In the intervening 7 years, he has been, a schoolmaster, lawyer's clerk, soldier, and poacher!
None of the above are proven however.
The 'poacher' story, arose when he was supposed to have been beaten out of town by the Lord Lieutenant of Warwickshire for stealing his deer!
Shakespeare died in 1616, the Lord Lieutenant did not put deer on his estate until 1619.