Susy's place is a brothel frequented by the migrant farm workers to whom George and Lennie are introduced at the beginning of Of Mice and Men. Old Susy herself is described as a likable character who often makes jokes without every talking dirty. The establishment is also a place where men can go and have drinks even if they do not want to engage the services of a prostitute.
Susy assures her patrons that her girls are clean and that "there ain't no water in [her] whisky." Her place is described as clean with nice chairs. We are told that Susy has five prostitutes working at her establishment.
Susy's place is the opposition, in business terms, to the establishment run by Clara. Clara's is more expensive than Susy's place, and the men don't like Clara as much as Susy because she doesn't make jokes with them and because she charges more.