Marin Pt. Reyes, Gary Fisher HiFi Pro, Easy Racers Gold Rush recumbent, Cannondale F600
Seems like what he's asking isn't too far off the mark- basically you're getting all the parts he's added at a small discount, and the frame for "free". That's assuming the small dent in the fork is as harmless as he says it is.
It will take a chunk of money to add brakes and the drivetrain since you don't have the parts available, probably $200 or more unless you can buy both derailleurs, brakes, BB, crankset, and chain used or at some sort of discount. Closer to $250 if you need to add cables and housing. At that point you'd be into it for $400 or so, which still wouldn't be a bad deal- IF the rest of the bike is in good condition.
I've had 3 Cannondales with the headshoks. They provide a limited amount of travel but are simple and light weight, just fine for the street and modest XC riding. Just beware that it may be difficult and expensive to get them rebuilt, as Cannondale no longer provides dealer support for the older models. Skip this bike if the Headshok is in bad condition (loose or no damping left).
I don't think a good deal - the frame is solid and it's a good bike but you can find similar vintage complete bikes for <$300. This guy needs a lot of work. You're going to spend multi-hundreds to get it running.
If you really like it, as rnorris mentioned, look closely at the headshock, if it's in bad shape, pass.