How Donald Trump profits by keeping his home base in Trump Tower

On a holiday weekend featuring headlines about Donald Trump's profiting off of his impending presidency, one smaller example of those gains lies in Trump's own high-rise home. 
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Last week, President-elect Trump announced his wife, Melania, and their youngest son, Barron, would be staying at their current home in Trump Tower New York for a few months after the January 2017 inauguration to allow Barron to finish his school