I am owed 12,000, but the situation has lingered for nearly four years. Is there a statue of limitations in obtaining money owed to me?

All jurisdictions have statutes of limitations on collecting debts, which differ from state to state.  Usually the limitations period runs from the date the debt was supposed to be repaid.  If there is no date specified for when the debt is supposed to be repaid, it is usually construed to become due either upon demand, or within a "reasonable" period of time.  In New York, where I primarily practice, the limitations period is 6 years from when the debt was supposed to be repaid (unless the contract to repay the debt says otherwise).  I don't know what the period is in D.C., or even if D.C. law would apply (it might not if, for example, you loaned money to a Maryland resident).  If you are beyond the applicable statute of limitations, there may still be some (rare) circumstances which can extend the statute of limitations in some jurisdictions, such as a written acknowledgement of the debt or where a debtor is estopped to rely on the statute because he lied to induce the other side not to file suit in a timely fashion.