Simultaneous closing is a real estate seller financing technique, whereby the private mortgage note created by the seller is simultaneously sold to a note buyer on closing.
This depends on how early in the process the note buyer gets involved and whether there are closing issues with this transaction.
The seller's main motivation for using this technique is to obtain cash on closing or shortly after, instead of receiving the proceeds from the sale over a period of years.
[1] The buyer's motivation is to obtain more lenient financing from the seller, especially when credit issues are or have been a problem.
He has to make sure that he doesn't get too involved in this transaction and thereby appear to be acting as a lender, which he usually is not.