Kevin O'Leary: Don't spend money on things like coffee if you're paying off debt – 'that's the key' to financial success

"If you have student loans, if you have debt, if you have things that you're paying interest on, you have to pay those off first," investor Kevin O'Leary tells CNBC Make It, especially before spending on luxuries like coffee. "I've said in the past, don't spend money on coffee if you can't afford it. That's the key."