There's a number of communities within 15 minutes of North Kingstown so it depends on your preference. If you like the small downtown sort of feel, you could rent a place in Wickford or downtown East Greenwich, both about 10 minutes away from Quonset (assuming that's where he'll be working). East Greenwich can be expensive though.
I believe the state mental health agency is in Cranston, try the state jobs website for more information (
Job Opportunities in Rhode Island State Government). There's also Butler Hospital in Providence, Bradley Hospital in East Providence and probably a lot others that have mental health programs.