Simcity has commercial buildings (selling processed products), and factories (selling raw materials: metal, wood, plastic, etc.).
What makes the most money is metal, then wood, then plastic, and so on, until, finally, chips. But for it to be profitable, you have to be continuously selling raw materials, so metal, and even wood, are impossible: there would be no material time to do it. Note that metal comes out in just 1 minute, and at the other extreme, chips come out in 7 hours. You can see in the chart table below, how with metal (theoretically) after 24 hours of continuous buying and selling, 864,000 coins would be earned... but this is in theory, it is impossible to do so.
What's the trick then?. The timing of your time. With examples you can see it better:
- If you are going to eat, put into production Chemicals (which is 2 hours), and when you come back from eating, sell them all.
- If you go to sleep, put in all the factories, Chips (which is 7 hours), and when you wake up, sell all the chips.
- If you have to work for 4 hours, put in all the factories Sugar and Spices, and then, when you come home from work, sell them all.
- And so on...
In a very short time you will see how with your tax income in addition to this trick, you earn more than you spend, and you can save and expand your coins with little effort.
Video of how to put the factories at maximum production:
Video of how to sell the products produced in the factories:
Table and Chart of the sales (with you buying and selling 3 times a day chips -which is the least profitable-, you will get about 30,000 extra coins a day).