Bite the bullet and go for one of the new RTF trainers that come with some sort of flight simulator. The flight sim is invaluable and will save you a bunch of money on crashed models, a RTF trainer will have everything you need except field equipment. Whether it's electric or nitro depends to some extent on how much you want to spend on that field equipment and your interest in a particular power source. If you Mustang is nitro powered, it may be to your advantage to buy a nitro powered trainer and get used to how things work and how to tune an engine.

Look around for a local club, they're usually more than happy to help out new guys and may have someone interested in selling what you want.