Funding the president’s wall should not be terribly difficult, especially for someone who is familiar with raising funds for viable public projects.
Congress should float a bond offering to raise the $20 billion or so that will be needed to build the wall.
These bonds will be of the “revenue anticipation” type, that is, to be repaid from future revenue generated by the funded project.
The anticipated revenue will come from Mexico, exactly as the president promised. Congress simply needs to authorize the bond float.
The bonds will be retired as Mexico remits the money.
Bond-rating organizations will certainly rate the bonds (whose interest will not be subject to U.S. income tax) very highly given that the President himself has given his assurances that Mexico will pay for the wall.
This will give the investors the confidence they need to purchase these bonds.
Thus, I expect that these bonds will be fully subscribed even at the low interest rates such highly-rated bonds command.