Sketchy Employee Situation?

I talked to a business owner who says that all of his employees have social security numbers, but he's never had to verify them because he has 10 or less employees. He also doesn't pay them overtime, just a commission of some sort in addition to their hourly wage. Sounds very sketchy. Any ideas?

If I buy the business and they turn out to be illegal, I assumed I'd just have to fire them (and the problem is replacing them at once and likely at a higher wage). Do you e-verify the employees in diligence?