All you can do is ask as many questions as possible, and hope that you get truthful answers. Fortunately they're a sound engine design that will go forever if the oil & filter have been regularly changed. Budget time (& money) for a valve clearance check, shouldn't be too bad unless they've been allowed to close up through neglect (in which case valves and seats can burn out - more expense, though the engine's basically an early FireBlade unit so spares will be plentiful. Listen to see if the valve gear is very quiet, and establish if it's difficult to start when hot - those can be tell-tales of tight clearances). Brakes, suspension and bearings may be tired, but they're easily refreshed or improved upon. If the price is right it could be a good doer-upper.
