My wife's electrician frequently "works for free golf". Does that count?
John is right. The "business part" is the most important part of any business. The difference between a business and a hobby is how well you collect the money.
If I was starting out today I would have some kind of integration between a smart phone and my desk top computer so I could be accounting for every minute of my day and every part I used that could be reconciled and billed out of my computer. You could also use that to dispatch your calls and track your response numbers. (call customer, on site, cycle time etc)
We did this at IBM in the 80s using the Motorola Portable Terminal (the precursor to the blackberry)
so I know how well it can work.
I am not sure who offers the package but I have to believe it is out there.