tl;dr There is a 600 million to 2 billion USD annual market related to crossing the Mexico-US border. Allow temporary work visas (say 3 years) to take over this market and use the money to boost the US Border Patrol to build a wall of eyes, not a physical wall.
President Trump of the United States of America,
cc President Peña Nieto of the United Mexican States
Today, Wednesday January 25th 2017, you are expected to announce your plans about building a wall between the United States and Mexico.