Everyone who's saying it costs to much to enlarge the farms should keep in mind that if they are a high enough level to unlock the purchase of a bank in the store (level two hundred something) it will make coins every day since all of its products are non-ingredients. All you have to do it keep them refilled every 3 or 4 days and sell the stocks, certificates of deposit, etc. along with any other non-ingredients.
You will also want to keep in mind that the latest update changed the way working the factories for other people worked. When one clicks one factory's blue button it automatically closes and goes to the next one. They did this precisely because they are well aware that not everyone can spend the money to get trains that increase the speed.
