There are three major obstacles to prompt payment: waiting until your purchaser gets paid by the owner; disputing over changes, delays, or other issues; and paying a high cost of recovery through the legal process. A contract cannot guarantee payment, but a well-drafted one improves your chances of being paid.
In order to maintain control of conditions of payment, ensure you use your own forms for contracts or purchase orders. Don't begin work until you have the best contract that you can get. Instead of agreeing to pay the contractor when he gets paid by the owner, require payment within a specified number of days. Contracts should also include some agreement for arbitration should a dispute arise. This can save much time and money that would be wasted in litigation.