A career is an area of work an individual chose to concentrate on more regardless of how long they've worked. A job is not an area of work they chose to concentrate on. You build a career over time based on the jobs you've held. A job can be a career and a career can be a job. You can turn a job into a career. It all depends on the individual. If an individual has done the same job for 5 to 10 years, they can call it a career if they want to. If someone has been a Hitman for four years, he can consider himself a Professional Hitman and he can say that's his career (who the heck would want to?). It doesn't matter how long he's been doing it. See, it's all up to the individual in question.