Not Really, as it is the USA who wants to build the wall, not Mexico.
Not Really, as it is the USA who wants to build the wall, not Mexico.
Impracticalities aside, I think it's a moot point since Trump isn't talking about having the Mexican government sign a check. If the Mexican government does nothing, then seizing remittances could fund* the project in less than a year**. The Mexican government can avoid that by agreeing to improve their own border security, but that would for all intents and purposes be them paying for a metaphorical wall. We may not end up with literal slabs of concrete on the border but Mexico would at least be carrying their weight, which is all anyone wanted in the first place.
* Remittances are estimated to be ~$24 billion per year, which is well in excess of the highest wall cost estimates I have seen.
** Ignoring for the moment that a 100% remittance tax would eliminate wire transfers overnight.
I can tell the Government I will not pay a cent for "Syrian" refugees all they long, but they are still going to take part of my paycheck for taxes and then I have no control what they do with it.
Same principal with the wall.