Neat bikes.
As you probably know, the Nighthawk series was a style excercise of the early 80s that sort of combined the 'cruiser-ish' look of the CB-Custom line with the semi-sportiness of the CB-F line. Not quite as cruiser-y as the Customs but not as sporty as the Fs. The N-H 450 followed that theme and there was a definite 'family' visual relationship between the 450 and the larger 650s and 750s of the early 80s - paint schemes, tank & seat shapes, wheels, etc.
They were available, in various years, with a whole host of different motors - a SOHC 450 twin, a DOHC 550, a 'leftover' SOHC 650, a 'new' DOHC 650, a DOHC 700 and a DOHC 750. Most all were chain drive, but at least the 700S was a shaftie.
As for the 450 motor, it is/was the final evolution of the CB400 Hawk motor introduced in 1978. It's a twin, it's counterbalanced, it has 3 valves (2 intake, 1 exh) w-screw and locknut adjusters and has CV carbs and electronic ignition. AFAIK, it has no real weaknesses at all. It soldiered on as late as 1987 in the Rebel 450.
That should certainly get you started.
As for your specific one, it'll all depend on what shape it's in when you go see it, and if you/he can get the title issue squared away.
Good luck with it, whichever way you go.
Kirk