Its the last part of the question that's the trick it says ''He didn't know how to split 5 dollars between the three guys so he decided to keep 2 for himself.''
It does not specify which 2 he kept, the 2 dollars or the 2 homeless guys!
because he had to split the money evenly between the two he could have given one dollar to the homeless man he did'nt take and kept the rest of the money for himself(by proxy). that's how I reasoned it out, I mean It's a relatively open question isn't it, i mean the dollar could have went anywhere, but if he took 2 guys he could give them as much money as the guy they did not take(1 each) and by the proxy since he took the 2 guys he owns what they own so the money given was divided evenly between the 3 guys but since the bellhop owned 2 he really got 4 dollars while the last guy walks away unowned with the dollar.