While English is not the official language of the United States, it is the most likely language that you would come across. Therefore, you as an employee will need to be able to communicate with my tenants, and those wishing to rent a residence from the company. Therefore, a good grasp of English is a requirement. While it is preferred for it to be your first language, it can be a secondary language if you have a sufficient understanding of the language.
You also must be understood even if you speak English. Some people may have an accent that might make it hard for some people to understand. This will be inefficient, and cause delays in addressing an issue. With that said, any accents shouldn’t be so prominent that it will be hard to understand you.