As Fannie Mae prepares to vacate its iconic headquarters with a move to downtown Washington in 2018, the buyers of the colonial-style building are mulling over plans on what to do with the four-story, close to 250,000 square-foot property. Roadside Development, in a partnership with Sekisui House, bought the building situated on about 10 acres last month.Before making plans on what to do with the property, Roadside is seeking public input in the form of community meetings and online outreach. Roadside founding Principal Richard Lake said the firm wants to sit with the community and spend time with them to get ideas, just as they did in other nearby development projects.