You can count on his supporters to hear what they want. Within days of his deporting them all he was yeah, let’s spend billions to round them up and we will the good ones back in, which means pretty much all of the them. His website doesn’t even say he will deport illegals anymore except the criminals.
He literally cannot do most of what he says he will and why should he? He would make his liberal friends very unhappy.
Mexico will probably end up paying for the whole thing - even rounding up the Mexican Citizens who invaded the USA.
Move the border south and grab their land. Then you can build a proper impenetrable border.
Also, take Cancun and put it in a lockbox for good measure!