We give aid to Mexico. The easiest thing t do is to reduce the aid and redirect funds to build. Of course those who want the illegals to come in will not do this. I think Trump will do it and characterize it as Mexico paying.
Eliminate the aid altogether and redirect it to the cost of providing illegals' medical and educational expenses, as well as to cover the cost of health care for American Citizens who acquire exotic and/or deadly diseases not seen in the U.S. for generations.
By the way, Caldecabron, how do you deal with Mexican fleas and head lice?