Hello! 
Example: I am drawing a house, walls etc. Another person is going to work on same project, drawing a staircase house. In this case the problem is that the roof surfaces of the main house I am drawing is connected to the roof surface of the staircase house, that another person (if possible) is going to draw. If the roof surfaces was not connected I would suggest that he just draw the staircase house in a independent project.
But can I send my project to him, let him draw the staircase house on my project at the same time as I continue to finish the main house - and then later we can combine his work and my work in one single project???
Or can he draw the walls for the staircase house in another project, and then afterwards we can combine his project and my project or at least copy his work into my project???
Do you understand what I mean?? 