Typically, you are identified by the nature of your last degree, and ME usually has more job options than NE. That said, unless you take a lot of undergraduate courses, you may find yourself not quite fully prepared. As an NE, I presume that you have had a lot of heat transfer, probably some fluids, and things like that. But, where do you stand on the machine design topics (statics, dynamics, mechanics of materials, vibrations, theory of machines, machine design)? These seem to me like the place you may still be short, even it it is not fully evident to potential employers.
Also, what do you mean by "purchasing" an NE degree? This is a curious way to describe this.