Create a wall between the US and Mexico

I think to control the immigration of illegal immigrants to the US and to increase security between the US and Mexico, and stop drug trafficking, we should build a wall on the US-Mexico border. After doing the math, we could build a wall (which is 15 yards high and 9 yards wide across the 2000 est. mile long border or 3.52 million yards long) for less than $300 billion. I'm sure many Americans would be willing to do this work for free or we can higher cheap Mexican workers. We should take action and protect America from foreign invaders. Mexico could be secretly planning on taking over the US through using illegal immigrants to sneak Mexican spies to take over the Government. We should take this into consideration to protect man kind.