Hoffy has a good point, its just that I didn't suggest it because this is an analog site and I didn't want to get flamed as well . Digifail is a fantastic polaroid to test your lighting with if nothing else, doesn't of course mean you escape a decent light meter though. It does mean that you won't potentially burn good film, especially 5x4 film.
As said above, there are cheapies. I wouldn't get 'cheapies' if you want to do this long term. A good decent branded system with a decent set of light modifiers will be a lot better long term as well as being a system you can build on. However the choice is there.