A client funded one of my sourced deals and then asked the seller to knock the sourcing fee off the price before close.
The agreement said the fee was earned at contract execution, not at close, which is the clause that saved it. The seller had already signed, the fee was already owed, and the buyer could not restructure the price without the seller agreeing to unwind a separate obligation. The deal closed at the original numbers. Without that execution-date language, the buyer's request would have just been a price renegotiation dressed up as a bookkeeping question, and I would have been the one absorbing it.
The clause that tends to get skipped is the one that defines when the fee is earned, separate from when it is paid. Earned at execution, paid at close is a two-part structure, and both parts need to be in the same document. If the agreement only says "fee due at close," the buyer has a technical argument that nothing was owed until the closing occurred, and if he kills the deal or renegotiates the price before then, the fee renegotiates with it. The execution-date trigger removes that window. It also matters when a senior lender later kills a deal through an approval clause, because you have something to point to that predates the lender's involvement.
The one thing that still creates ambiguity even with good execution-date language is whether the scope of the sourced deal was met. If your agreement defines a qualified deal as one matching a specific buy box and the buyer later claims the property did not qualify, he has a hook to argue the fee was never triggered at all. The fix is a written confirmation of scope acceptance from the buyer, dated before the earnest money goes hard.
What does your current sourcing agreement say about when the fee is earned, and does it separate that from the payment date?