You can also get coins from Funny Money caravans: costs 100 to send and returns 90 to 150 coins after 2 hours. If you need sugar, flour or apples for making food, it may be better to send caravans for those, but when you don't, you might as well send caravans for coins. The returns appear to be evenly distributed between 90 and 150 so 1/6 of the time, you lose 1 to 10 coins but the rest of the time you earn between 0 and 50 coins. Sending 6 at a time, I've never seen a time where I lost coins across the 6.