Nothing wrong with that. We already have legal provisions for people to do EXACTLY that through LEGAL immigration and work-visas. That only covers a small percentage of the ones currently here. The rest (the vast majority) simply drive-down wages for LEGAL citizens. We currently have over 12 million able-bodied American citizens out of work. There is NO job that Americans will not do provided it pays enough to take care of the bills and keep the family fed.
The 'labor-shortage' that these illegals are filling is a fictitious propaganda ploy used by the CRIMINALS who hire them to avoid paying a decent living wage to their employees. There is NO labor shortage. There is only a shortage of employers willing to obey the laws of our country and compete in the free-market for the services of US citizens.
With a Guest Worker Visa program, the type of work allowed is specifically spelled out.
Right now, the Congresscritter looks the other way as 5,000 Mexicans sneak over the border because his agribusiness constituents want 5,000 tomato pickers.
The illegal Mexicans then figure out that is is just as easy to illegally get into the high paid construction industry as into the tomato picking industry. So, the agribusiness needs 5,000 more illegal Mexicans the next picking season, and the next and the next.
The cycle repeats endlessly and, right now, we have total anarchy.