[quote=@Song Book]
[@Dark Light] Who would be working at this guild? 
[/quote]

The guild is essentially a job agency, they take on work and give it out to its members, everyone will be expected to take on some of these jobs eventually.
There are a very broad range of tasks that are handed to the guild but guild reputation can dictate and influence the majority.

As for internal jobs there will be the guild leader.
He organises the work that the guild accepts and puts up the jobs on the job boards. 

The rest becomes purely optional depending on the type of guild you barter for.
There could be a care taker.
A bar maid.
A cleaner.
A stable hand.
An accountant.
Resident bard.

The list is endless.
They all come with pros and cons. Cons mostly being cost.