He doesn't want to teach anymore; he wants to do business.
Tips
mistakes
Note the pronunciation: 教 is read jiāo (1st tone) in 教书, meaning 'to teach.' When 教 means 'religion' or 'teaching' as a noun, it's read jiào (4th tone), as in 教育 (jiàoyù, education).
usage
教书 is a verb-object compound (离合词). You can insert elements between 教 and 书: 教了十年书 (taught for ten years), 教什么书 (teach what subject).