You cannot legally purchase earlier versions of AutoCAD or AutoCAD LT. The current version is 2013.
If you do obtain LT 2010 there is a good chance that when you go through the online registration and activation process you'll be denied. Your software will stop functioning after 30 days. You will have no program and you'll be out whatever you paid for it.
You would be better off saving your money and downloading the free 2D version of DraftSight by dassault systemes. It is remarkably like AutoCAD.