BUY IT!
Worry about anything else later!
£500 is scrap value! you CANT go wrong at that money!
Lots of pottential areas to look at, and of the breed, mid eighties motas are a bit of a PITA when it comes to spares, as they made a lot of changes in a short period and lots of bits were deleted from the parts catalogues; but a two door should share most parts with the earlier models, which now being 'desirable' classics are better supported than external hinge four doors; NOT that this one sounds like it should NEED much attension!
And, its no different to any other 'classic' car really, its just that we've enjoyed a long period with Rangies being dirt cheap and second hand spares plentiful....
As said tho, at that mileage, probably coming up for an engine over-haul.
I did my 84 auto a few years back, and keeping it 'original' was a twelve week project, completely tearing the engine to the bare block, and LOTS of cleaning to get rid of the 'black-death' carbon deposits in the cam-gallery and avery where else, before reboring, and rebuilding with new cam, new tapets, new timing chain and gears, heads skimmed, valves and seats ground, new rockers, rocker shafts etc etc etc etc , down to the hoses to plumb it all back in at the end... a tad over £700 worth all in, and Worth every penny! Really 'crisp' and very powerful.
Daunting, when the car, like yours only cost £500, but soooooo nice!