Actually, if I was going to be in the U.S. without a work permit I would opt to start a business over trying to get a job, it's far safer. As an employer, I use the USCIS e-verify system for everyone I hire as most employers do, and it's pretty tough to trick that. I'm also required to collect a panoply of documents for every hire and keep them on record, as is every employer in the U.S. As a potential undocumented worker, I'd have to find an employer who was OK with knowingly hiring undocumented workers since otherwise my chance of being caught is high, which would be scary for me.
On the other hand, if I start a business I'm in charge of doing the verifying so I don't have to worry about that. Customers don't care and have no responsibility to check work permit status, whereas an employer does. As long as I pay my withholdings and file a tax return every year the IRS isn't going to bother me and there's no avenue short of Arizona style stopping brown skinned people to check for papers that is going to expose me as long as I follow the law everywhere else. The entire logic (which admittedly is debatable) behind the firewall between IRS and DHS is that a ton of money comes into Treasury from undocumented workers and Treasury doesn't want to make their job harder by making people afraid to pay taxes and do withholdings.[/QUOTE