Not sure what version you are using etc. and the exact method you want to use but try the following :-
Start the projected elevation as you describe (sideways on) and draw a line that you wish to be horizontal in the final view (i.e. vertical in modelspace ?). Then go back to paperspace and enter the model space viewport. From the drop down menus select :-
Tools
New UCS
Object
Then click on the left hand/bottom end of the line. Now go to drop down menus again and select :-
View
3D Views
Plan View
Current UCS
The elevation should now be rotated in your view but if you go back into model space everything will be as before.