Building the wall is treating the symptom.
Let's treat the disease by fining and jailing those that employ the illegals.
The illegals will not come in the 1st place if they know there wasn't work for them.
Then we could take the monies from those fines and save the 5 billion construction costs and repair our infrastructure while providing work for our citizens that will be paying taxes. Win win win.
At the very least try this before wasting that money if it doesn't work you can build the wall later if necessary