This is called being "Judgment Proof" I believe.
http://en.wikipedia.org/wiki/Judgment_proof
Essentially the court and the person suing them can do nothing if the person does not have the money but the person who owes the money is still liable if they ever do receive money or assets in any form. Wage garnishment I believe is only legal in some states meaning if someone is Judgment proof it is not difficult to work the system and stay that way if you have one against you.
EDIT. I was wrong only 3 states do not allow wage garnishment.
http://en.wikipedia.org/wiki/Wage_garnishment So if the person is "Judgment Proof" and gets a job you could motion to garnish their wages at the rates listed on that wiki page.
Also as far as the child thing as far as I know children are not liable for any of their parents debt unless they choose to take on the debt. Even if say your parents give you their house upon their death, if it is not paid off it is your choice to receive it. Anything non asset related (other than taxes I believe) is absolved completely unless the child chooses to acquire that debt. Of course creditors have first call on all liquid assets from the estate before the Executor is allowed to deal with the rest of it.