General opinion is that a side job is one that supports the main income of an individual, often times perceived as something that brings little money to add to what you make from your day job. If Mr X earns better from a side job when compared to the income from his career option, does the side job still qualify to be called a side job?
I think the size of the main job and side job is from the formality of the job, many people work formally with a small salary but have a larger income from business or other sources, of course he thinks that the side salary is a supporter of the main salary so that if it happens The bad thing is that with a side salary, the economy oru financial is not disturbed.