I answered this question the other day, but I don't mind repeating myself:
Easiest way to make money is to buy as much property as possible, at least until youre making 10k every 5 minutes. Then, before you finish playing for the night or before you go to sleep, put a rubberband around the joysticks of your 360 controller(the single rubberband connecting the two so the point towards each other. Your character will walk circles all night as your game runs while you sleep. Wake up the next morning and you'll have tons of gold to buy more property. I did this trick while making 40k every 5 minutes and after I slept one night I woke up the next morning with 8.5 million gold/ Easy.