Echoing what Nate said to some degreee, used 35mm film camera bodies bring very little, unless they are Leicas or something similarly exotic. Do you know what lenses the seller is including? Also, which flash unit?
There's an important point here WRT external flashes and APS-C cropped sensor cameras: The canon 580EX was first speedlite to recogize the difference between an APS-C, APS-H, and full frame/film body, and then adjust its output accordingly. Older flashes won't do this and will be calculating for a wider angle. I can't say specifically what the real world effects of this incompatibility might be (I've only shot with the 580EX and 580EX II) but I do recognize it as an important consideration. I have used "manual" flash units, and in situations where I have a stationary (patient) subject, they're fine. It takes time to adjust the camera's settings with respect to the flash's output power and distance to the subject. I would not want to have to monkey around with anything less than a fully compatible speedlite when dealing with a subject like a small child. YMMV.
Lastly, Canon may have in fact introduced some additional speelites between the release of the 580EX and 580EXII that are APS-C compatible. I have no idea which ones, but I suggest investigating the model you're considering if you're not sure.