As a seller of a property a Coinciding Settlements Contingency is worse than a Sale of Home Contingency in a couple of ways.  You must be aware of these differences when explaining the contingency with your seller or you could be in for a very bad experience.  Here are the items that make the Coinciding Settlements Contingency good for the buyer but bad for the seller.

No Kick-Out Clause - A seller has no opportunity to have another contract bump the current contract like you can with a sale of home contingency.  (Keep in mind I, this is the contract in the D.C. metro area.  The contract you use may be different.)

1. No Continued Marketing - Because our MLS system has only Under Contract/No Kick-out or Under Contract/Kick-out, the MLS system is setup unfavorably for the Coinciding Settlements Contingency.  It's already bad enough to not be able to leave it in the system as Active (MRIS will fine you if you do), but you can't enough mark it as having a kick-out.
2. No Information until it is too Late - If you happen to get stuck taking a Coinciding Settlements Contingency, here is a scenario you just might face.  Settlement day is here.  Your clients have spent $5000 to move to their new home.  The house is vacant.  They made all the repairs and cleaned it professionally.  Maybe they drove up or flew up from Florida just for the closing.  The lender has assured you that everything is fine.  You show up to settlement and there are no loan documents, no money, no buyers.  You call the other agent.  The closing on the Buyers house did not go through this morning.  They will not be closing on their house.  They will not be buying your clients house.  They will exercise the Coinciding Settlements Contingency Clause.  Sorry.  Good Luck.

Whoops.  Didn't see that coming.  Now your clients will look at you and say "I want the earnest money deposit".  No can do.  The Buyers didn't do anything wrong.  The buyers agent protected his clients, you did not.  You can't keep the EMD.  Not only are you not getting paid, you look like a complete idiot because you let this happen.

Fortunately, you can prevent this from occurring without blowing the deal.