Depends what you mean by transact. An empty account can make about 23 transfers in 5 days so if the purpose of the account is to save or spend STEEM/SP/SBD (with a modest pace of activity), that may easily be enough. For using any of the social apps it probably isn't enough, although even that is enough to lurk, make the very occasional comment, and/or place a few (2-3) votes per day (which would express opinion but not count toward rewards since the account has 0 SP).