Obviously you must be the top earner for each job type, this means you have to successfully complete the job. A failure in the mission does not count towards this achievement.
To avoid failure (AKA Venkman Victories), you must do the following for that respective mode:
Containment - capture at least one ghost
Destruction - destroy one cursed artifact
Survival - Survive one wave of enemies
Protection - Activate all three PKE towers
Slime dunk - Capture at least one slimer
Thief - Finish the match with one artifact remaining
My strategy to get the top earner is to start with the slime blower. Throw out a trap and slime dunk a few ghosts into your trap at the beginning of the match. This should give you a $2-4,000 lead right from the start. Then from there make sure you assist and get combos with everyone else that traps a ghost. If you see someone trapping a ghost quickly wrangle them with your own proton beam so you can get the assist/combo. Slam dunking ghosts into your own trap also gives you a bonus for cash over those that support you.
The job types that you need to get top earner in are: containment, destruction, protection, slime dunk, survival, and thieves.