When Gene started his window-washing business, he wanted to keep things simple. He liked the idea of being his own boss and the possibility of leaving the business one day to his son. He chose the type of business that was easy to start, allowed him to keep company profits, and not have any special taxes. Gene's financial resources were limited, but so were his concerns; after all, "he was the business." Gene's business is most likely a(n) __________.