Unwillingly paying customers is a difficult business to build, and they could go as far as making you do their work for them in advance before they pay you, sometimes, they never pay, and keep cooking up stories on why.
I think viewing money as fuel could work here too. We might have enough fuel but if we can't drive the vehicle to our desired destination, then the fuel isn't really the problem here.
That's the problem of some businesses/services.
For example the price of an artistic work of art can be determined by the buyer. This is bad on the artiste who is bringing the service. Unwilling customers spells doom for a business or business person.
That's why most businesses of this kind are inherently unsustainable. Unless a platform of sorts is created but that too, makes the skill more or less commodity and price fluctuates depending on demand and supply