It's been a while since I played this, so my apologies for the lack of a thorough walkthrough on this. From what I remember:
1) You need to work at the train station cleaning
2) Somewhere along the way, you will hear that you can buy some trinkets in the Industrial area of St. Petes, at the storage facility (it's the same facility as where your character's real father works). I think you need to go during the week, during the day, so it conflicts with school a bit, but you can go during a school break.
3) Come back and sell the trinkets at the train station - not sure when, but there are certain times.
4) Get harassed by the police, and profit?
I think there are more elements to this story that just this, but this is the core of it.