There are good arguments for and against, but I think the most solid argument yet is that you can complete the fence but otherwise intended immigrants will just find another way. The old refrain goes "We need to secure the border..." which would require a lot more live, ground level surveillance to be deliverable. The challenge of a low energy barrier is no match for a desperate person with unlimited energy to make ends meet. You must fight fire with fire; desperation with desperation.
If the federal government was interested in both immigration solutions and job creation; they could take a lot of unemployed, angry blue collar workers, train them and transform them into the vigilant local border forces at a much lower cost than escalating a fence which damages the environment and fails to deter immigrants, while stimulating the economy! It's essentially the same group of people which became the Minutemen. Currently, they volunteer, without power to apprehend based on the conviction that a Mexican immigrant is a national interloper "taking their job". They would do their job providing two for one solutions at the border - provided their new superpowers do not expand to oppress and surveill American citizens.
There is one misconception which requires some temperance.
Most migrants are independent contractors. They run their own businesses and employ members of their family to make it work. Oftentimes, they find work for others. If you want to get started - get on the next truck headed for Home Depot. If that's not for you - keep searching the trades. If it gets tough, look into that job out of county; which may be little beneath your pay grade.
If you're unemployed and want to stop illegals - start asking DHS for a job to do just that.
It's the one job not available to undocumented immigrants.