Escrow Company

Escrow companies are a neutral third party that holds money to be paid upon performance of a specific contractual event.  Often used for "hand money" or "earnest money" in a real estate transaction.  Escrow company accepts money from buyer and pays seller when transaction completes.

There are many escrow companies.  Real estate title companies often provide the escrow service.  Price for the service is small.
Escrow service fees as low as 0.89% of the purchase price.


Wikipedia entry

http://www.gaebler.com/Opening-an-Escrow-Title-Companies-Business.htm
"... client contacts will be limited to the attorneys, lenders and real estate agents that represent buyer/sellers, and most of your communication will take place by phone or email."

Search for escrow companies

Typically requires a state licensing process, along with adequate financial backing and the manager needs several years of experience in the industry.
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201305 SecureHandShake.com appears to be gone.
Contractor Transaction Escrow
escrow & contract management service that includes a guided and structured process with transactional security.
Disclosure of documents, escrow, dispute resolution.

It seems this could be built on an existing payment engine (paypal or whatever) and add on the account management, paperwork, and workflow approvals.