Just keep your eyes peeled, people sell their cars on here from time to time. I know there is a discussion going on right now about a g24 for sale. Also, Fatboyslim is selling some of his projects, not sure exactly what stage they are in but he does some amazing work.
Before you decide to take the plunge you should know that building one of these isn't a matter of buying the parts and bolting everything on. To build one of these cars you have to be comfortable with fabricating/custom building most of the car. This means doing a lot of welding, fiberglass, etc... If this is something that you can do or want to learn how to do then by all means join the club. Just know, it won't be easy, especially if you don't have a mentor to teach you some tricks.