If you start a business doing something you've done before as staff in a company, you end up doing the same work with more stress and less free time and competing with others who saw the same opportunity to not work for the man.
If you come up with a great new idea for a service, then you spend more time selling than doing the actual work. It is harder than it first appears to get people to grok something that is truly new and different.
In both cases, chasing payment for services rendered consumes more time and energy than what I had planned for.