As long as it is disclosed to the corporation it can be done if the company so desires.

I'm writing a story where the CEO of a company wants to purchase a decrepit old building and turn in to a hotel. I know Berkshire Hathaway has helped finance deals with other companies, but I was wondering if it would be a conflict of interest if a CEO invested some of his own money to acquire a 20% or so stake in the project?

Is that legal for a publicly traded company?