Ratters or Rat-catchers are people who use Ratting Ferrets to control the pests like Rats, mice and other small rodent creatures. To try and prevent the spread of dieases, and to prevent damage to food supplies. It is a profession as old as civilisation itself, wherever food is store rats will try to enter and consume the stored grain or other foods. If the rats and other vermin weren't dealt with people could starve or get sick from the contaminated food sources. Not a lot as changed since those early days, the vermin still a menace and the Ratters still do the job of keeping the swarms down to a managable level, but there still a Lot of rats out there in the sewers of the city, They are very much the domain of the rats.
No real qualifactions are needed, but an ability to handle animals which helps with handling of Ferrets and other animals used to chase down the rats and kill them. There is the other way and have some low level Druidic ability who can talk and command the vermin to leave. But that route is a lot rarer as druids tend not to want to join the ratter's guild, and anyone doing their work and not of the guild might wake up one night to a pile of rat's in the bed with them.
Payment & Reimbursement
The Guild set the charges, depending on size of building, how big a problem the vermin are, and also the district the works in. As while a job in Dawnward and a job in Rosefrost Ward can be the same size of job, but Rosefrost is an area full of money and the Guild can charge more because of it.