What is the purpose of a minimum charge?
For me a minimum charge is the minimum i am willing to earn doing a job. As even the smallest job will take a certain amount of time, taking in to consideration driving to the job, looking at the area, talking to the customer about what they require, offloading equipment, setting it up, doing the job, collecting payment, loading equipment back in to the van, collecting payment, processing payment, driving to the next job. Not to mention, owing the van, equipment, chemicals, obtaining the knowledge to be able to do the job, advertising, insurances and the umpteen other things i cant think of at the moment.
What should that minimum be set at?
That means knowing how much it really costs to run your business and turn a profit. Unfortunately many people don't know the answer to that question. This isnt always the case, but i think many under value themselves and as a result go out of business prematurely.