There's an angle to this that I appreciate spiritually - making sure your client is conscientious and committed - and an angle that is legally and ethically hig

There's an angle to this that I appreciate spiritually - making sure your client is conscientious and committed - and an angle that is legally and ethically highly risky. Instead of putting contracts in the drawer and setting yourself up for future legal peril (and dissection of any implied contracts you may have entered) figure out if your client is trustworthy and liquid early. If there's risk, structure contracts to manage the risk, such as a short-term engagement leading to a longer / higher-value contract that locks you in. If you can't agree that structure you probably shouldn't take the contract in any case. If they don't pay the first bill, fire them like any good contract will allow. Don't wait five months.