If you are moving for a full year (and only a year) then definitely try to find a place before you move as many places will want a 12 month lease (though group houses can be more flexible). If you don’t know many people in DC then a group house is a great way to start with a social circle. If you know people in DC then ask them if they have recommendations/know of a house looking for someone. A ton of spots in DC turn over via word of mouth.

DC is overall a safe city so ignore the other comments. Crime is an issue but it’s typically very targeted. DC is great and it’s far better than living isolated in the burbs.