Access database for Veterans

I’m doing consulting for a Vietnam Veteran who belongs to more
than one veteran’s organization. He wants to combine all the
organizations that help veterans, around 200 of them, so that a
veteran can look up national, regional, state, and local chapter
information including a list of contacts at each level. Has
anything like this been done before that I could look at as a
model? Is there an existing database that I could use as a
starting point? If I have to start from scratch, do you have any
suggestions that would make it as efficient as possible to create
and maintain?