I need to draw a very simple family as shown in attached picture , that has only two parameters (EXIST and EXIST ) , can anyone tell what family should I start with?
I believe that this would best be accomplished with two separate Line-Based Detail Item families. You could then create a schedule to report the distances and Exit #. You could use the Comments parameter to enter a designation value so that each instance of this report can be separated (filtered by the schedule) and thus have it's own schedule.
Here is a related thread with more info on how to accomplish this:
Here is an article from Revit wikihelp that covers this topic.