Venus and Serena’s dad and first coach, Richard Williams, didn’t just teach them how to hit a perfect forehand when they were kids. He also taught them to be businesswomen, even if they didn’t fully realize it at the time.

When the rising tennis stars were kids, their dad “had us listen to foreclosure tapes on the way to practice and tournaments,” Venus tells CNBC Make It. That means learned about how to make money buying foreclosure properties.

Most of the information went over their heads, Venus adds, but that didn't matter: "It was just the mindset that he created of thinking for yourself, thinking outside the box and [having an] entrepreneurial spirit. My dad was all about all of that.”