There is a very simple concept on how to implement jobs.
CUTSCENE: Protagonist sees "Help Wanted" sign and inquires within. A person says there is a job opening.
GAMEPLAY: A mraker appears along with on screen prompt explaining about jobs: "You can apply for this job by stepping into the marker" appears also.
ACTION: STEP_INTO_MARKER: Protagonist is given the uniform pertianing to the job and a person tells him "changing rooms over there". Protagonist comes out of changing room in uniform, first task is assigned to him.
CONTROLS_OF_JOB: Protagonist is given a quick on screen prompt of controls and how they function. Protagonist is also given the "Quit for the Day" option control.
GOAL_OF_JOB: Protagonist does the required tasks asked and each job becomes a little more challenging or can vary in difficulty.
QUITTING: Protagonist presses the necessary button to quit job.
CUTSCENE: Protagonist walks past the desk where a person says "See you next time".
GAMEPLAY: Protagonist is free to walk around again; the marker has disappeared and will reappear next day. Protagonist also has on the uniform that he was using during the job. This outfit can now be stored at his safehouse. In order to access the job, the protagonist must be wearing the uniform pertaining to his job. Only one job can be applied to at a time. The protagonist can opt to quit his job, which will become available later unless he is already with another job. By doing so, the player will lose the uniform.
This was just a simple idea of mine that R* could do. I'll expand on this later.