Find a formerly rich guy looking to keep the power on. It's getting tougher now with the dot.bom craze over but check around. There are nice cars to be had for way too little money. Check e-bay... Be careful there (and everywhere else for that matter)
www.clubcobra.com seems to have a ton of Superformance cars for sale. Look here as well. You will find car values somewhat higher here as we own better cars.
Be Patient. I first looked at my car in Sept. If you can wait until December to buy a roadster people who haven't sold may be getting desperate. If it looks too good to be true it probably is.
That said you have come to the right place. There are people here who will look at your potential purchase and give you an unbiased opinion, help you through the registration process, help you find insurance, etc. etc.