Roundabout

Buy every piece of property in the game. If you play long enough, you'll get enough money to do this, and of course, the property itself can reward you with money. If you're struggling to make money, be sure to periodically visit your properties to gather money. In particular, the most valuable properties tend to give the largest money drops; the memorial gives you over 100 dollars per time it goes off. The shortcuts between the upper and lower half of the city in the second area are also handy to buy, as you're likely to drive past them pretty frequently and it is easy to snag both.