Willis lives 45 minutes from the Innisbrook Resort and Golf Club and took advantage of an invitation to compete in what is his sixth appearance on the PGA Tour this season. His best finish this year has been a tie for 26th place at the Bob Hope Classic.
He had a one-shot lead over defending champion Retief Goosen, Jonathan Byrd, Rickie Fowler, Jim Furyk, 2005 winner Carl Pettersson and Jeff Maggert.
Maggert was the seventh alternate and got into the tournament only because Vijay Singh withdrew.
"I was debating whether to go ahead and come on over and I just took the late flight last night," said Maggert, who lives in the Houston area.
Willis birdied four out of five holes to open the back nine.
"I was fortunate enough to get off early before the wind really started kicking up," Willis said. "I was constantly putting at birdie, so made it pretty easy."
Steve Elkington, Ross Fisher, Jeff Quinney and J.B. Holmes were tied for eighth at 68.
John Daly, who has made the cut in each of his last two tournaments as he attempts to rebuild his career, shot a 1-under 70 and was tied for 21st place.