If you want the illegals in the country to leave employers must be targeted.

This targeting is important because the employers of illegals are undercutting those employers that follow the rules, stealing business by using those stealing jobs (from Americans, often those most desperately needing the job, and those that immigrated legally). It is also important for those immigrants that went through the agonizingly long process of legal immigration to be allowed entry into the job market without an illegal worker stealing their opportunity.

Only special criminal sanctions will work! If I were writing legislation it would look like much of the drug statute arena. What did not work in drugs will work with employers of illegals. For example, jail time (make the employment a felony), seizure of homes, factories, equipment, cars and other property. So the meat packing company that hires them gets raided and the factory is seized, or the landscaper trucks and equipment plus maybe a home or car, and each is tried as a felon. And what about the legislators and others with the maid, gardener, or other worker? Take their home and car then prosecute. The seizure and criminalization did not work with drugs because the profit margin is too large...but employment of illegals offers much smaller margins thus the risk far outweighs the reward.

What will happen when the jobs dry up? First the cash drain to other countries stops. Then many will return to where they came from since they know they are here illegally and the incentive to stay has been removed. Illegal immigration slows considerably and becomes a pure security issue to be dealt with severely.