There is a multi-unit search, however it is found under the advanced search options. There are two links on the home page for the advanced search. The first is found at the top, just under the title bar. There is a tan bar that runs horizontally that has several links. The link on the second row, on the left side, is called "House Plan Search". This will take you to the advanced search options. The second is slightly smaller found just under the width and depth boxes in the basic search criteria. It says Advanced House Plan Search. I've linked this text to make it easier to find.
There you will find a section called "General Architectural Styles". That section will have the Multi-Unit option.
Woody
Sales Associate