Panhandling is a great way to make money off the books, tax free. You are only limited by your lack of imagination. You also can make money off the books by babysitting, housecleaning and dog walking. Another way to make money tax free is hosting a garage sale or lemonaide stand.
Things like home improvement tasks and cleaning are the most popular things to do. Write an ad in the paper that you will do house cleaning. You could also mow lawns and rake leaves.
sheff for home, shoffer, distribution of advertisement papers in certain community or locality, officers for election proceedings, nanies, baby seating ect. are some employments which we can call as off books employments.
If you can tutor, that's a commonly cash-in-hand endeavor, as are yard maintenance, house sitting, babysitting, or shuttling. If you have an expertise, like computers or plumbing, advertise those services.