So when you had unlimited money, you built the things you needed without worry and soon spent less and less as you needed to built infrastructure and other things that take little money. So, while it was active, you built your city and it grew to make more profit from the added buildings making more money. At least not making enough profit to spend money very quickly and you found yourself twiddling your thumbs often waiting for money to accumulate so you could buy certain things.
I'm sure when you turned on infinite money you were at or above making a profit.
