Paul,
In the skilled trades her in the Midwest, its called "progressive billing". It also requires that a contractor be licenced, bonded, and insured. Contractors can still end up getting stiffed by non-performing subs, which is why there is insurance for such an event. Subs can get stiffed by the contractor holding a 10% retainage at the end of the job (sometimes forever), which requires a visit to the county courthouse to resolve. Contractors usually win over subs, because they have the money and the future work.
The thing is- this isn't a 15 million dollar municipal works project. It isn't hardly even a car (from the pictures). Business on ebay is conducted long distance, and the buyer really has very little protection in the event that something goes south. On a car restoration project with so little to start with, I can't really imagine anything going right. On a restoration, you are buying reputation. Does anybody really want a cobbled up speedster restoration?
If you had an original, basket case speedster, and the capibility to restore it right, wouldn't you just go ahead and do it? Even if you had no money- you'd find a way. The fact that he either can not or will not finance the project on his own gives me pause as to the reliability of the seller as a subcontractor, as well as his dependability as a restorer. Complete speedsters go for BIG bucks.
Let the buyer beware.