Finding duplexes/small apartment buildings

My name is Patrick and I’m a complete newbie at RE investing. I would like to research small apartment buildings for sale my area, the MD suburbs of Washington, DC and also some of the small cities on the Eastern Shore of the Chesapeake Bay. (The MD side.) Primarily, I am seeking information on duplexes and buildings with four to six units at most. Single family houses with an additional apartment or in-law suite also interest me.

I already searched the forum archives and didn’t find any posts that closely match what I’m seeking. The older posts mentioned loopnet and costar, which are fine, but I’m not sure that they will include the kind of properties I’ve described above based on brief visits to those sites. (Although I have not subscribed to either one yet.)

I welcome all suggestions.

Realtor.com has a multi-family search option in advanced options. Your best bet is to find the site for your local assocoation of Realtors or the website of most real estate offices would have a MLS search feature.