House suitability: From now on, all houses need to have a piece of solid furniture (e.g. a workbench, table or dresser - something you can place things on) and a bed (instead of any piece of comfort furniture). NPC-only version of bed can be crafted using workbench and 15 wood.
Guide: The guide will no longer spawn on world creation, but will require suitable housing to spawn.
Merchant: Not only will the merchant require 50 silver to spawn, his house also needs to contain a chest.
Nurse: The nurse's spawn is no longer dependent on health, but on having reached character level 5. Furthermore, she requires an alchemy table for making potions.
Demolitionist: In addition to requiring some form of explosives, the demolitionist will also require a keg to fulfil his needs for beer.
Arms Dealer: The arms dealer knows that presentation is the key to good sales, and requires the player not only to have some form of gun based weapon but also a chest.
Dryad: The dryad requires both the mayor to be present and for you to have killed one of the normal mode bosses. There are no further requirements for the Dryad.
Clothier: The clothier requires both the mayor to be present, and requires a loom, on top of requiring Skeletron to have been defeated to free him from his curse.
Goblin Tinkerer: The goblin tinkerer not only requires rescuing, but also requires the mayor to be present and have both a chest (of any quality) and a workbench in his house.
Mechanic: The mechanic not only requires rescuing, but also requires the mayor to be present and have both a chest (of any quality) and a workbench in her house.
Wizard: The wizard not only requires rescuing, but also requires the mayor to be present and to have bookcase, chest and skull candle in his house.
He sells the books to craft melee passive abilities.
A training dummy and a chest (of any quality) in his house.
Level 10 melee skill.
She sells the books to craft thrown passive abilities.
An alchemy station and a chest (of any quality) in her house.
Level 10 thrown weapons skill.
She sells the books used to craft ranged passive abilities.
A practice target and a chest (of any quality) in her house.
Level 10 ranged weapons skill.
He sells the books used to craft magic passive abilities.
A bookcase and a chest (of any quality) in his house.
Level 10 magic skill.
Required for the spawns of some of the original NPCs and the Carpenter.
The mayor is a sign of a progressing village that requires some organised administration for further growth.
He sells books.
The Guide, Merchant and Nurse.
A bench, a chest (of any kind), a chandelier (of any kind), and a dresser in his house.
He sells doors, chairs, signs, tables, dressers, benches, mannequins and looms.
A chest (of any kind) and a sawmill in his house.
Required for some of the new NPCs,
He has the highest housing requirements of any NPC.
The Mayor and Dryad (he really thinks she's something).
A golden throne, a golden chandelier (of any torch color), a toilet and bathtub, a dresser (needs to keep up appearances for the Dryad), and a chest of gold quality or higher.
Skeletron must be killed.
She sells all possible potions (the greater healing/mana potions will only be available when hard mode is unlocked) and gel. Note: this won't make farming for ingredients redundant as the perks gained from increasing the alchemy skill are huge - it just means you won't have to grind for really rare ingredients, or bother making any at all once you've hit level 50.
An Alchemist's bench and a chest (of any kind) in her house.
He sells a full collection of golden tools, weapons and armor, jesters arrows, shurikens and throwing knives, and also sells anvils and smelters (a new work item capable of returning 80% of metal bars used in making tools, weapons and armor).
A furnace, anvil, and a chest (of any kind) in his house.
^*Uploaded these prior to recieving them ingame; Sprites might not match -but im fairly certain they are right -