City of a Thousand Towers
A merchant guild is much like a noble house, except that the merchant family has lower status than a noble family. However, it also has more opportunity to act outside of the social strictures, as do their retainers and servants.
For starting purposes, you can use the same options as for the noble house member, retainer, or servant, but the character will have more freedom to act without regard to the merchant house.
As a member of a merchant house, you can expect the head of family to demand significant tithes, contribution of time, or duties.
See Noble House for details.