Well, I know people don't remember it, but there are still eminent domain lawsuits in the courts from 13 YEARS AGO, when the Bush administration tried to build one. Any attempt by Trump to take away farmers' and ranchers' land would simply add more lawsuits, which would still be going on 13 years from NOW, so the wall can never be built as Trump envisions it. There is also the problem that the Rio Grande makes up part of the border between the US and Mexico, so he would have to decide whether to grant Mexico sole ownership of the
Rio Grande, thus turning quite a bit of American territory into Mexico, and robbing farmers and ranchers of their sole source for water.
The wall is merely another of Trump's fantasies, which he is currently using to bully those who have the nerve to disagree with him. The only solution I can see is for Congress to pass a budget bill with a 2/3 majority on both Houses so that he cannot veto it.