To Quest or not to Quest, that is the question. I have most of the facilities and it's hard to keep up, because new ones are introduced continually. I have completed maybe 30 plus Quests, and was impelled to purchase new facilities to finish maybe 3 or 4 times. A couple were available for coins! Don't know how I missed them, but I did, and noticed that some facilities that formerly require cash are available for coins.
I like the Quests; they afford me the opportunity to make coins easier than all the farming - just try keeping 14 farms going. I play daily just to store goods and harvest common facilities.
The Billionaire