I found an interesting idea to make money in idle mode, using industries. Make around 700000 cash (possibly using the loan from Sapoboi in the mission with them Narizians), then find a cheap industry in whatever town, the only condition is that the town has to produce food, water, and the raw material your industry will use. Leave all your people in a school, then go to the town with the industry you chose, buy the industry, deposit a few thousands in cash. then activate advanced trading to buy a few thousand tons of food, you won't be able to move but you won't need to. Then go to the travel mode, full speed for a little while, leave the tab open for as long as you want (if you have enough to eat 'f course).
Made roughly 44000£ in 5 minutes with the jacket industry I bought from Kivi, if the income is regular, which would be surprising, I can make 528000 an hour. Obviously, this can only work well if you don't have animals..
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