There is a statue that you can go to in the area before the museum. You can only hit it once a week.
If your brain is good with puzzles then the warehouse.
Paperboy is easy and you can get a fair bit of money.
High speed chase gives you the most but can be infuriating.
Easiest way to get money would be to dig holes in the desert. you get money, items, and fossils. Sell the items and duplicate fossils.