My short answer to your question would be that all of the areas within 20 minutes of Berry Hill would be a safe bet for appreciation. Woodbine and the neighborhoods off of Thompson Lane and the northern part of Nolensville road would be very convenient, but these are transitional neighborhoods, and you may not find all of them "decent" (that can be a very subjective term). Donelson and Hermitage may be more to your liking. You can find accomodations in south Nashville and parts of Antioch of the fringe of your 20 minute drive to Berry Hill that you like. If you are willing to purchase a condominium, there are smaller units available in Green Hills or the Music Row area that may fit your needs.
The key to a value-oriented purchase is to buy equity up front. Our team specializes in foreclosures and investment properties. There are a lot of good deals on the market right now, particularly if you are willing to consider purchasing a foreclosure, a HUD home, or a bank short sale. You can gain even more equity if you are willing to work with a fixer upper or do some cosmetic repairs.
Good deals in this market move quickly, and I would be prepared by pre-qualifying with a lender as soon as you are serious about making your move.