Very interesting question.

How many people out there drop off a % when a customer wants to pay you cash. Then when the work is all done they want to write you a check?
Can you tell us how you normally would work this out with the customer? When do you tell them this and how do you document it or is there no documentation?

Or when you have a contract that states 1/2 the money up front and the rest of it upon completion only to get done with the job and they say we will send you a check. I'm thinking about tacking in something a little extra for those customers who want to try too screw me over. Whats your opinion?
Maybe you could break it into thirds? Would that help? 1/3 at signing, 1/3 at mid point and 1/3 at completion? Or would that be too much? Could you have maybe the final payment via credit card?