You can only loan one item at a time to any player. If the item is not accepted by the player you can collect your item again after 7 days. If the player accepts your loan during these 7 days then you can collect your item when the loan time is over.
Each loan accepted is logged in the history tab. There you can find the name of the item and loan that you accepted, along with a status icon which indicates that the loan was successful.
The owner of the loan will receive in his mall inventory a special loan item that is intended to be a cheque, were this item will give you the amount you have requests for the loan.