Is there housing on or around the Vassar campus for married students?

As for on-campus housing, the Res Life website is not that specific but I'm going to guess no; probably the only way around that is if you're both upperclassmen and happen to be married, then you can put in for "gender neutral" housing.

Off-campus, yes. There are apartments in the area which are outside the purview of Vassar as far as I know, so that's an option.