To set the matter straight what we do is called Commercial Lawncare or Commercial Landscaping. Although folks frequently use the term professional to describe themselves, the United States Government sees things different:
§ 54.1-111. Unlawful acts; prosecution; proceedings in equity; civil penalty.
2. Making use of any designation provided by statute or regulation to denote a standard of professional or occupational competence without being duly certified or licensed.
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In not so many words, you need to be Certified or Licensed as a professional by the Department of Professional and Occupational Regulation.
And I looked long and hard, but I didn't see what I do here:
http://leg1.state.va.us/cgi-bin/legp504.exe?000+cod+TOC5401000
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Far as how it looks with a rider?
... Who defines what professional looks like?
I go topless in the summer, some say that looks unprofessional.
Me, I don't care... Better than wearing shirt uniforms and sweating all day.
This is your business, you decide your appearance. IF you are somewhat careless in your approach, some your customers will be, too - Birds of a feather flock, I like a little lack of care myself (less nit-picking the bs).
I think what works best is be yourself, do what YOU would do OR do what you would expect of someone IF you hired someone like yourself to work on your own yard, for example.
Hope that helps.