In my honest opinion, I am afraid CAD without being an engineer or have a 4 year degree will not be an option, with today's job market. Employers have their choice of the "cream of the crop" when it comes to potential employees. In most cases that I have seen, the engineers will do their own drawings. Not to mention there are many of them out of work as well. Many of them are well versed in most of the major CAD software programs. Then you have the case like me where as you would be starting out and I have 15+ years using most of the new CAD software packages.
In my opinion, if you want to back to school get your M.B.A. There are many jobs opening with people with a masters degree and experience.
In answer to your original question, different companies use different software, usually depending on the size. Larger companies usually use 3D solid-modeling packages such as Autodesk Inventor 2008,2009 Pro-Engineer, Microstation and Solidworks. Smaller ones may use only 2D packages Mechanical Desktop Autodesk 2009.
Hope this helps and Good luck in your decision.