Ask yourself why they really removed the fairing? Was is dropped? Or was it really someone wanting a custom look? Check fairing, headlight cluster, wiring loom, mirrors, main square bracket and two side brackets are included, if you want to convert it back. Check the mounts on the frame haven'tbeen ground off too, to give a 'cleaner cafe racer look bro'.
Check past MOT advisories have been sorted. If not, it gives you a clue the seller hasn't maintained it well, or just bodged things to make do. If so, you'll keep uncovering more crap that'll cause you grief in the future.
Other things to check:Front sprocket nut, check if the recall fatter nut has been fitted, or at least the original nut hasn't come off in past and it's since been bodged. It's common to find it's been welded on (which might explain why the chain not being sorted out...)
Check back brake is not seized and is good. It needs regularly cleaning and TLC or it can catch all the road crap and seize up. Many swap on a blue spot FZS1000 rear brake in such cases.
Sounds like downpipe will need replacing, not a show stopper though. £200 should get you a set of stainless pipes. But fitting can be a bitch if the header bolts snap - so check if they look like a mess of corrosion.
Check condition of all water hoses, if any cracked/brittle - there's no good source of silicone replacements.Check if still original rubber brake hose - if so they'll need replacing at this age, but that's a cheapish job (~£60 parts + ~2hrs labour)
Rear shock could be due refresh if still original (red one). If not hugger fitted, check if its all crudded up and corroded down there.
Check other usual suspects, no oil on forks, check oil colour in window, check brake pads replaced, age of tyres, rust in tank, any random crash damage etc.
Either way, be fussy, if it all smells like a bodge-fest, just walk away, there's plenty of Fazer's about to choose from.