Apparently, the border is 1,933 miles long.

1,933 miles / 800,000 applicants ~ 0.002417 miles per applicant ~ 12.76 ft per applicant.

In other words, each one of us just needs to build a 12.76 long section of the wall (and make it maybe 10ft tall). The wall would be built within a week and it would cost way less than $30 billion. We will volunteer, buy the bricks, concrete, etc. needed to build our section. I am sure there are some DACA recipients that are civil engineers or contractors that can help us with any structural challenges or problems we might face while building.