For around 15 years, he ended up selling life insurance for Canada Life, mainly to former union members and colleagues, the only place he could find work. A For around 15 years, he ended up selling life insurance for Canada Life, mainly to former union members and colleagues, the only place he could find work.( Misplaced modifier)
B He ended up selling life insurance for around 15 years for Canada Life, the only place he could find work, selling mainly to former union members and colleagues.(correct)
C For around 15 years for Canada Life, he ended up selling life insurance and sold it mainly to former union members and colleagues, in the only place he could find work.(misplaced modifier)
D He ended up selling life insurance for around 15 years for Canada Life, mainly selling it to former union members and colleagues, at the only place he could find work.(misplaced modifier)
E For Canada Life, he ended up selling life insurance for around 15 years, the only place he could find work, to mainly sell to former union members and colleagues.(misplaced modifier)
Will go with choice B.
Regards