The Wall that Mexico paid for... I mean the US...no I mean the wall that Mexico will eventually pay for!!!

I was reading a blog written by Phuong Nguyen titled IS IT WORTH TO BUILD THE WALL? I found it very interesting. The first thing he talked about was the cost of the wall. It started out as a mere 4 billion and eventually went up to about 20 billion. That is a lot of money! It is ok though because we are not paying for the wall Mexico is!!! But wait there's more!!! We are going to pay for the wall and Mexico is going to pay the US back. Even though they have said more than once that they are not going to pay for the daggone wall. So now on to plan B. We will slap some tariffs on them and they will pay for the wall that way. I am not an economics major but I am going to take a shot at this. The US wants to buy an avocado from Mexico. Mexico charges the US $5.00 dollars for the avocado. The President slaps on a 20% tariff: $5.00*.20=$6.00. The US wants to buy another avocado from Mexico. So now Mexico charges $6.00 for the avocado. Mexico still has $5.00 and the US has $1.00. Can someone tell me again who is paying for this wall? Phuong also went on to say how can this money be better spent. Well since the president loves the veterans how about he use this money to solve the homeless veteran problem in America. I bet 20 billion could solve most of all the homeless issues in America! Phuong also stated the rhetoric that the wall will prevent people from coming over illegally. It might make a small dent in the issue but most people over here overstay their visas and I am not sure how a wall is going to help with this. Also the amount of immigrants coming from Mexico and Central America is decreasing while the numbers from Asia and Africa are increasing. So again I am not sure how the wall will help with that. The great supporters of this wall are the ones that say gun control/reform will not work. That these gun laws will not prevent people from committing crimes with guns. I am just curious why that same argument doesn't seem to work for the wall. I asked my mother what she thought about the wall. Her response is the wall to keep others out or us in? Her answer totally crept me out!  I think that it was a Berlin Wall reference and I choose not to be that cynical and hope that there is no truth to her words.