What form of business ownership did troy smith select when he first made the decision to be an entrepreneur?

Troy Smith decided on "sole proprietorship" form of business.  A sole proprietorship is a small business where there's really no legal distinction between the person who is the owner and the business itself.

Troy Smith opened his first drive-in business in Shawnee, Oklahoma in the early 1950s -- a root beer stand called Top Hat.  In 1956 he added a partner (so his business became a "partnership" then.)  Later he added many franchises (expanding the business further), and eventually his company became a publicly traded corporation.  Oh, that corporation and chain of drive-in franchises is now called Sonic, which has been the name of the Smith-founded restaurant chain since 1959.

Troy Smith retired from managing the Sonic Corporation in 1983, and passed away in 2009, at age 87.