When you insert a file into an other the 0,0 of the inserted file will be at the extremity of your mouse.

This is important when your inserted file becomes a block in an other file.

You can have your file "in situation", for example in a 2D drawing you can draw an horizontal line from 0,0 and offset it to have the Y direction towards the real elevation in a drawing, then when you ask for the ID of a point it will indicate with its Y the elevation; if you use the DIMORDINATE command it will lay a dimension indicating the elevation.

Eventually, see my file FEET-METERS.dwg inthe CAD/BIM Blocks library right here in the site.

It explains alternative units on dimensionning but is also usefull from a general configuration of a drawing.

When you set a viewport in the paper space and have its lower left corner at 0,0 you will have an identical print setting on each of your files.

 

Be aware that you can use the BASE command to specify the location in a drawing that will be used as its insertion point when you Insert or Xref it into another drawing.  It does not need to be 0,0 [though that is the default], but can be any location you choose.

 

One other effect of where you draw things in relation to 0,0 is that unless you specify otherwise, that is the location from which Hatch patterns are generated.  Hatch patterns that have elements at non-orthogonal angles or other complex characteristics can, depending on how many decimal places they go to in their definitions, have the relationships between elements get skewed as you get farther and farther from the origin.  That potential problem is avoided or at least lessened by keeping your drawing generally in the region close to 0,0.  But you can still overcome that if you need to be far from 0,0 by setting the SNAPBASE System Variable to a location in the middle of your content [even if only temporarily while you draw a Hatch, as you would anyway for some patterns where the positioning matters, such as brick coursing], and Hatch patterns will be generated from there.  In later versions, you can even designate the origin point for individual Hatch patterns within the drawing of them, or afterwards in the Hatch editor.

In model space ( don't know in paper space ) your limits are in absolute coordinates is -9.99999E+99,-9.99999E+99 in negative coordinates and 9.99999E+99,9.99999E+99 in positive coordinates. 

John please tell us more about THE way to go.

I'm working with AutoCAD since 1995 and I learn new things each month.

You can't learn everything in the first decade but you will developpe your utilities conformably to your needs.

There are a lot of ways to deal with AutoCAD and each one of us will use and developpe what is good for each one, and let alone what is not needed, at least up to the moment that it will be necessary to learn more about a specific subject ( or continue to work slowly with an old method, this is not a problem ).

Karl, there are nowadays so much informations on the internet that you will be abble to learn more each day.

I have learnt much with CadForum than with an other way.

Have a nice day.