I'll say you better list it here for auction with a hidden price(~Pending Loan Amount) which can be verified by other people at the end of the auction.
If auction crosses that hidden price you can take your loan amount from it and send the rest to the owner.
In case it doesn't cross the hidden price then the auction will be cancelled and you keep the item.
You can discuss with the borrower to sell it and keep the money from the auction even it is unable to cross the hidden price with the rest of the money still payable by the borrower.
Hidden reserves will always scare bidders away here.
Price checks are the best way go go about it here, most people use previous auctions and collectibles knowledge when replying.