If he owns any property or has any income, you could potentially collect the money by either putting a lien on the property or garnishing his wages. You should sue him--for amounts under, say, $3,000, you may wish to file the suit yourself in small claims court (acting as your own attorney); for larger amounts, you should probably get a lawyer. Once you file a suit, he may pay, or at least offer to settle for some amount; if not, if you win the lawsuit, he may pay (or offer to settle) at that point; if he doesn't, you may be able to collect by garnishing wages or putting a lien on property (or if you know where he banks, you can levy on his bank account; or if he owns valuable personal property, like jewlery, art, vehicles, big screen TVs, etc., it may be possible to have the sheriff seize those and sell them for your benefit). Worst case, even if you can't collect immediately, a judgment can potentially be enforced for years to come--such as if he does inherit money.
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