Nothing to do with residency.
Home visits are done at many schools. The purpose is to forge a partnership between the teacher and the child's family. No need for snacks or preparation.
Expect the teacher to introduce herself to you and your child, and to ask you what your goals are for the year, and if you have any particular concern.
Some people like them, some people don't. You can choose to opt out.
This Foundation underwrites the hoe visiting program in many DC schools, both DCPS and charters (teachers are paid for their time to do them, and there is training and so forth involved).
http://flamboyanfoundation.org/focus/family-engagement/parent-teacher-home-visits/