Q: What’s to prevent Congress, after Trump inks a deal, from passing legislation that takes away access to the money he could use, and then overriding his veto.. ?
Nothing if, with the collaborationist GOP, they have the votes to override his veto. Of course, at that point, it is time for a general uprising against a government that is the declared enemy of Americans and is colluding with invaders bent on the destruction of the US.
The two-thirds vote needed in both houses to override. I don't see them having enough.