Player Guilds are associations of Players/Characters that form their own guild. Factions are not the same as Guilds. Factions are Knights of Solamnia, Wizards of High Sorcery, Dragon Army, etc.

Guilds can create & share guild vaults, purchase a guild house, have a guild merchant (Sells items as a merchant and adds proceeds to guild vault), purchase guild branches (for selling item from Guilds Merchant & Accessing guild vault around world), create their own ranking & naming system, their own respawn location, as well as several other features.

To start a guild as a guild master, a character must meet the following requirements:

Level 40.
Charisma of 18 or Greater.
Intelligence of 18 or Greater.
10 Ranks in Persuade Skill.
Leadership Feat.
15,000 gold pieces.

15,000 sounds a bit cheap

Not so cheap considering the gp ramp I'm using. Gold will be the most rare treasure drop there is. Mundane items will be the most common, and merchants have a huge markdown on buying items. It'll balance out, and can be tweaked as needed.