The deal allows the debt-ridden club to repay a £1.3m loan from Panama-based money-lenders, the ABC Corporation, which is secured against Loftus Road.
Rangers already owe ABC £10m from the deal which took the club out of administration in 2002 but needed the extra cash to pay an outstanding tax bill and stave off a winding-up order from HM Revenue and Customs.
The money from last week's Cook transfer will allow the club to pay off the short-term loan and give chairman Gianni Paladini more time to find new investors.
Rangers director Nick De Marco said: "QPR were faced with a winding-up order in July. If the club had not found a substantial sum of money to pay off before 4 July, the club would have been put in administration.
"Faced with that risk and the need to pay various other debts and on-going costs, the club had no alternative than to seek a short-term bridging loan.
"Nobody was prepared to lend the club the sums required in time, apart from ABC. It's not a great agreement for QPR but it was a choice between that and administration. QPR are able to repay the loan now, in part from the proceeds of sale of Lee Cook."