Occupation is like something you are occupied with, and you're not necessarily doing it as a 'business' thing.
Employment is the same as occupation, and can refer to something you are employed in doing, but not necessary a job done for work or money
Occupation — any work for hire or employment through which someone makes a living
Job — any work for hire, regardless of the skills level involved and the responsibility involved
Profession — virtue of his fundamental education and his training in a certain filed of expertise, to apply the scientific method and outlook he has gained in the analysis of the problem its respective field, solving it diligently and accordingly.
"Jobs" are those positions that job-seekers are hunting; likewise, these are those vacant positions that company-owners want to immediately fill. In short, these are those public postings or notices without a skilled person yet.
"Employment" is more of a process. From a vacant job to filling that position with a skilled worker. The moment a job finds its skilled match, employment takes place.
A job can last one day.
A position can be occupied for a week.
One's occupation, on the other hand, is a long-term project. It's something one does for years and years. It can be financially rewarding at some point, and six months later - not so much.