The small one room house does not have much value, containing both a dining room with a bedroom and a large fireplace. There is an alcove that contains a room for a small table and chair, as well as a bookcase with a few books. An unlocked chest can also be found at the end of the room.
The Hero will receive this quest by finding Armand Christophe in the "Finding the Thieves Guild" quest. They will be tasked with proving their worth as a thief by stealing a diary from a house in the city. However, there are two other competitors, who also wish to join the Guild.
The Imperial Watch normally does not collect taxes from the poor at the waterfront; however, Watch Captain Hieronymus Lex has collected them this time. It is likely that it costs more to collect the taxes than the total amount of taxes received. Armand Christophe wants the Hero to take the tax money back, along with the tax records.
After completing "Taking Care of Lex" and fencing 600 worth of stolen loot, Methredhel or Amusei appear in any major city with a message from the Gray Fox. The cowl-wearing leader resides in Helvius Cecia's House in Bruma. Methredhel can be approached directly in her house in the Waterfront District.
The Thieves Guild has several rules (read the Thieves Guild rules). If the Hero murders or attacks their fellow thieves, they will receive a hefty fine. The Hero will also be fined for stealing from them.