Depending on how much of a back story you want:
Beggar's Nest was the poor district:
The Beggar's Nest is a district of destitution where most of the poor inhabitants live and work. To the north is a great graveyard, and there has been several records of undead attacks in this district. Under this graveyard there are unexplored tombs and crypts from deceased men. Packed with narrow streets and slum houses, this district is the most exploited of the five.
And The Dock's was the seat of most crime:
The Docks is the district most prone to criminality. It is ruled mostly by organized criminal leaders and thugs, often leading to black auctions and markets. With the main harbour to the west, many illegal wares are easily smuggled into the district, much because authorities do not have a very strong grip on the contemporal events. The district founds The Golden Apple, an inn, and Twenty in a Quiver, a local warbrand shop.
The City's Destruction:
However; much of the city was destroyed by the spellplague and the eruption of Mount Houtenow and has been rebuilt. Only three districts are available: Blacklake, which has been rebuilt in the area near Castle Never, the Docks, which remain largely unchanged, and the Merchant Quarter, which may be the remnant of the City Core.
I believe much of the poor have moved into the Southeastern quarter of the city core, or the ruined center of Blacklake District.It is conceivable that the characters have been recruited into any faction or guild in the city, or none at all.