He ABSOLUTELY should incorporate. If he forms an s-corp, he can have the corp buy a hefty insurance policy. Then, if he has an accident and is sued for more than the insurance will cover, your house is not at risk. The plaintiff will be limited to the insurance policy amounts. Think of the incorporation costs as a one-time insurance premium.
After he incorporates, he'll need to make sure he "observes the corporate forms," which means holding shareholder meetings to elect himself director, director mtgs to appoint himself CEO, and CEO decisions to hire himself to drive. Think of it as wearing many hats one at a time.
You can read about incorporating in various self-help books from the library. Then you can decide if you want ot try it yourself or if you want to hire a lawyer to do it for you.
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This is not legal advice and you are not my client. Double check everything with your own attorney and your state's laws.