We get asked this a whole lot in the foreclosure side of our firm.  We have also consistently said "no", as there is no reliable method of tracking closings in a county with 12 resident title companies and many small closing firms.  It is far easier to provide a product at a $20 date-down rate than a percentage of a potential sale. 

  This sort of structured deals probably have a very high failure rate and without an abstractor having some inside contacts to all of the possible parties, there is no way to find out when it closed.  Even if you find a closing item on the public record, you have no way certain method for determining if you "good client" handled it or if one of his unnamed "friends" did it in order to cut you (and probably a few others) out of some promises.   Whose gonna let you audit their books anyway?  (probably illegal)

  Best to protect yourself and get money up-front.