Mexico will not pay for the wall directly based on Trump’s plan, although through revised NAFTA trade programs, indirectly Mexico will pay for the cost of the wall through higher tariffs and taxes to export products into the United States.
Also due to quota limitations, of exports from medico allowed into the US, additional funds will become available by higher employment levels in the United States and income taxes paid as a result of those jobs.
The idea of building walls at the US southern border with other neighboring countries like Mexico is aimed at reducing the illegal activities of human smugglers at the border and the rate at what illegal immigrants are trooping into the United States. Donald Trump, before his election had made it clear he would ensure that Mexico pay for the wall and he has since been reassuring that Mexico will pay for the wall.
But the question is will Mexico pay for it?, the answer as of the moment is still no, because Mexico has never demonstrated any move that would hint whether the country will pay for the wall. Another reason Mexico will not fully comply is that, this project will be more beneficial to the US than to Mexico. Another reason why Mexico might not pay is that, Trump categorically said he would build a wall between the United States and Mexico very inexpensively, and this is raising the question that why would you have Mexico paid for the wall when you can build the wall inexpensively.