As opposed to just seizing it?
I would think the landowners would build first on their private property. Borrow the money and let the government(military) pay them back.
Except by Leftists (some with an R and most with a D behind their names) property isn’t seized without just compensation.
Corruption by Leftists has made the practice more common in recent decades, but it isn’t legal or moral.
There is a legal provision, and it is inevitable that it will be used for The Wall many times, that when a property owner has property that is legitimately needed by the government (Interstate highways and The Wall are good examples) and the property owner refuses to let go, the government can step in and ‘seize’ the property.
However the property owner MUST be fairly compensated.
Candidate Trump spoke about this a number of times during the campaign.
When the property is ‘seized’ for The Wall we will, of course’ hear endless sob stories of families ‘sacred grounds’ being stolen by Donald Trump personally.