Different quality.
Trust fund is a positive one you purchase to get a lifestyle + spending money every month which is what your thinking about.
Day job is a negative quality where you have to spend X hours (10, 20 or 40) a week working in order to earn Nuyen (?, 2,400 or 5,000. Can't remember the lowest level offhand) and can interfere with your runs which is the one I'm wondering about. This one is wages/salary for your work done and gives karma to spend at character creation.