Yes, the Prez can earn money while being president. So says a Democrat judge.

Hollywood Reporter:   Donald Trump is having quite a week. Not only did the tax reform bill pass — likely saving him significant money — but a federal judge in New York has just rejected a lawsuit that challenges whether he’s impermissibly benefiting financially from being U.S. President.
The Citizens for Responsibility and Ethics in Washington brought the lawsuit a few days after he became the country’s leader in January. The watchdog group alleged a violation of Article I, Section 9, Clause 8 of the U.S. Constitution, known as the “Foreign Emoluments Clause.” Specifically, the plaintiffs (which later would include those in the hospitality business competing with Trump’s hotels and restaurants) took issue with how foreign leaders were attempting to curry favor by booking stays at Trump’s Washington, D.C., hotel, how the Chinese granted Trump additional trademarks, and even how foreign-government-owned broadcasters were paying for The Apprentice.
In reaction to the lawsuit, the Justice Department argued the Emoluments Clause doesn’t explicitly bar “private business pursuits” with CREW responding this was an “extreme view” of the law.

 Yes,  the Prez can earn money while being president.   So says a Democrat judge.