And the trick here, too, is that BOTH mommy and daddy have to stick to the plan. I've seen it where the parents will decide to get tough, they make plans to get the kid out, deliver the ultimatum, and then one parent sabotages the whole thing at the last minute and says, "We're not doing this. I don't see how it's helping things to put our kid on the street."
Guess what? You don't help your 20-something offspring by letting them sit around your house jobless (or have a job and blow all the money on partying, DVDs, and toys). It's not love, it's sick. The only hope for straightening them out is for them to KNOW that they're really out of the house and done their last hustle on mom & dad.