Wow, that's super incredibly useful. Unfortunately, it appears to me that United States law doesn't mandate that sort of public access (even if blueprints are a matter of public record, that could just mean that they're filed in the basement of the county courthouse somewhere).
However, thare are some good resources I've found.
Residential house plans are super easy to get. My favorite collection is at
http://www.eplans.com/ which has thousands of plans and is searchable by house size and style.
One good way to get basic maps of larger public buildings is to do a Google search for "
fire evacuation map" or similar terms. These images could also be used as in-game handouts, representing the actual maps the Takers have to use, since they're more likely to be publicly accessible than blueprints.