[misterjangles]

I can see a client canceling a deal without paying after you have done work due to not having a contract. To actually use the work you produced and weasel out of paying with a "ha ha I tricked you into working for free" is really malicious. I would say that client would probably never have paid anyway. However you may force them to reveal their hand by signing a contract. They will probably try to find some other loophole, but at least you have some documentation that helps you to take legal action.

I have had client drag their feet on the contract and the down payment, but rush me to start. My feeling is that if you can't get a check when they are desperate for you to start, then it certainly will be difficult getting one after the work is complete.

The more eager you are for the gig, you may be more willing to agree to things. But definitely it's a always a good idea to be patient and make sure both sides agree to the terms before you invest your labor.