Whats the easiest off the books job to secure?

whatever it is that you're good at. in my case i get on average 2 calls a week to fix computers at friends and friends-of-friends homes at $25 an hour. I'm skilled, knowledgeable, a people person, courteous, quick and fair. My name and phone number has started spreading like wild fire.

the only thing else i could imagine, besides being able to fix something that's always broken, would be construction or tutoring.

EDIT:

When i was in college, i worked off the books as a bar tender and at a small mom-and-pop family diner. Just try asking an owner of a small place like that for weekend work.

babysitting, construction, or start a website and offer a service (my husband and I sell baked good online and resume) both do very well