My first reaction would be that you're probably better off going with one of the Dahon's. Nothing against the Brompton. In fact, I'm about to buy a used late 90's Brompton myself.

In your case, I think you'd be better off with a newer bike. Old bikes will always need tinkering to get them up and running, and parts will inevitably wear out quicker and need replacing. For instance, the rear hub that is on the Brompton you are looking at isn't made anymore so getting spares is going to a bit of a pain. Also, you will want to upgrade the brakes on the Brompton -- they are dismal on old Bromptons.

If you like the idea of small folded package similar to the Brompton, check out the Dahon Curve. $579.00 at Thor's site.

This is an aside: I hope you're not test riding new bikes at local shops, and then shopping on Craigslist.