You have to create the vehicles ingame, with /vehicle command (you need to have admin column to 4 on users table) and set their faction to 100 + jobId (defined on Constants.cs file)
Same with the mechanic job, you have to create the business ingame.
For thw driving school, you need to fill the questions & answers tables on the database.
JavaScript Client-side function: https://wiki.rage.mp/index.php?title=Entity::createModelHide
Example of removal of the street lamp within the place of spawn:
mp.game.entity.createModelHide(0, 0, 0, 100, mp.game.joaat('prop_streetlight_01'), true);