In The Great Gatsby, how long did it take Gatsby to make the money to buy the mansion?

After he meets Daisy once again in Nick's cottage, Gatsby
and Nick are left alone for a few minutes. In their conversation, Gatsby tells Nick he
earned the money to buy his house in only three years. This fits the timeline of
Gatsby's history as it unfolds. He had met Daisy in Louisville approximately five years
earlier, gone to war, and then returned to New York where he met Meyer Wolfsheim and
began his illegal, but quite lucrative, career. The chronology of these events indicates
that Gatsby is telling the truth when he says he became quite wealthy in only three
years.