The federal E-verify system is free and it works. If you want to prevent illegal immigration, control who can earn a living. Our lack of will to do so is what results in a large number of illegal immigrants living within our borders. E-Verify is voluntary for most employers. Only Arizona and Mississippi require all employers to use E-Verify. Seven states require public contractors to use E-Verify: Colorado, Georgia, Missouri, Nebraska, Oklahoma, Rhode Island, and Utah. State agencies must use E-Verify in Colorado, Georgia, Idaho, Minnesota, Missouri, Nebraska, North Carolina, Oklahoma, Rhode Island, and Utah. Federal contractors must also use E-verify.
That leaves everyone else. That is, most of the employers in the United States. You really don't have to do anything else on illegal immigration if you prevent unauthorized work.
Accurate Reality: We lack the political will to force employers to check for work authorization and thus stop the employment and therefore the economic ability of illegal immigrants to support themselves.