Know that you may be on hidden camera -- but it may not be legal. Video-only nanny cam recordings are generally legal, but they must be used for a reasonable purpose. Many states laws don't allow the use of nanny cams that also record audio. And several states require consent.
Be careful about "babysitting" teens. When teens drink or do drugs behind your back, you could be in trouble, too. If you knowingly furnish teens with alcohol, or should have known they were drinking while under your care, you may be arrested under social host liability laws.
Don't forget to pay your taxes. Babysitting income is generally taxable, though there are exceptions depending on whether you're under 18, how much money you made, and whether babysitting is your primary occupation, among other factors. In many cases, an employer may be legally required to (but chooses not to) withhold babysitter taxes, reports The New York Times. This area of the law can get complicated, so you may want to consult an experienced tax lawyer to figure out what applies to your situation.