Add heaps of friends so you have more chance of them vandalizing your Springfield and getting treats for cleaning up.
When you visit a friend, check to see if they have the money symbol above their graveyards or Mausoleums. Or even some of the Halloween buildings have the candy icon above it. If it does, collect those as you have the chance of getting treats/toilet paper/eggs. If they don't leave the Springfield and come back in a few hours and look again.
If they only have 1 building/graveyard with the treat/money symbol, collect it then go back to the neighbors screen. Re-enter that same Springfield and that same building/graveyard will have the symbol again. You can do this until you use up the 3/3 jobs.
Once you unlock Devil Flanders/Mayan Homer, make them start the 60min quest at the same time and every hour just collect and start the quest again. This is what I do with all my characters and it seems to bring in the most cash flow during the day.