The city of Decatur is a very desirable location and the market is strong compared with some of the other metro areas. Under $200K would be a challenge for a single family home. Have you considered a condo? Also, you could consider some other close-by areas of un-incorporated Decatur/Dekalb that might meet your needs. Decatur has their own police department and school system... therefore the taxes there are also higher to pay for those amenities.
A lease option in the City of Decatur for under $200K would probably also present a challenge since it is likely that such a property would sell quickly and the seller would not have to resort to offering it for lease purchase.
Moving before Christmas is certainly a possibility depending on your situation as a buyer.
I work in the City of Decatur and can advise you on the areas that will meet your needs. Please contact me if I can help. Knowing more about your lifestyle, your preferences, etc. would help me assist you in choosing the best location in your price range.
Good Luck In Your Search
As David mentioned there are several homes within the City of Decatur limits might work for you but are not what I would call "move in ready" and may need a bit of work. If you do have some flexibility on the location, there are a few neighborhoods bordering Decatur that are fantastic and a bit more affordable.
If you are able to purchase a home in the next few months, I would highly recommend that over the lease-purchase option -- the primary reasons are that interest rates are still low and you will probably have more negotiating power on the price and terms if you purchased the home outright.
If I can help with your decision or "house hunt", please contact me anytime. I've lived and worked in the City of Decatur for the last five years and know the area very well.
Have a good night...
Keller Williams Realty