If he did not finish the work he agreed to do and for which you paid him, you can sue him for "breach of contract." You can sue to get back the greater of 1) the amount you paid, but for which he did not do the work (e.g. if he did half the contracted for work, you can recover half the money) or 2) the amount it would cost someone else to complete and/or correct the work. He is legally obligated to do what he agreed to do and may not keep your money without completing the agreed-upon work. If the amount involved is less than the limit for your state's small claims court, suing in small claims, as your own attorney or "pro se," is the fastest and most cost-effective option.