A professional is a person who is paid to undertake a specialised set of tasks and to complete them for a fee. The traditional professions were doctors, lawyers, clergymen, and commissioned military officers. Today, the term is applied to estate agents, surveyors, environmental scientists, forensic scientists, educators, and many more. The term is also used in sports to differentiate amateur players from those who are paid — hence "professional footballer" and "professional golfer".
good ol' Wickapedia...wile it lasts anyway.
Now, i guess my way of thinking is, is there a model car building profession?