$5000 to $10,000 is the typical range for a Mini from good to outstanding condition. There are a few decent cars around for under $5000, but they're few and far between. Probably the most reasonably priced dealer in the Southeast with a large selection is Barn Hill Minis. They have a shop in Wales where all the purchasing and restoration is done, and they have a location in Orlando Florida where most sales take place. They can ship anywhere if you don't want to go to Florida.
I got my Mini from them last February after an extensive restoration/customization. It's awesome! Great guys with very nice cars.
Sorry for the commercial. If anybody is seriously considering a classic Mini in the near future, there's a very big Mini gathering in St Petersburg, FL from 3/7-3/9. There should be over 100 classic Minis attending and quite a few for sale.