Nice vintage bike you have selected there, you will get a lot of people interested in talking about it everytime you park it somewhere I'm sure.
With vintage bikes you have to remember they can be more expensive to run due to the constant maintenance you have to do on them and the parts can be hard to find (are there bike junk yards in your area?)
$650 is fine, but does it need anything at all? How old are the tires for example? Rust in the tank? Points? etc?