[Aerkuld]

Sorry.
There are probably people with far more experienced opinions on this than myself, but judging by the photo it 'appears' to be in good condition externally. If the interior looks as good as you would expect with the mileage, and the mileage is documented in some way then I would expect you to be looking easily in the mid to high teens. However, if the engine checks out and isn't leaking and if there are no other mechanical problems then you could be looking at the upper end of 20's. If you don't feel confident inspecting it yourself see if you can find one a handy Pelican in the area to give it a quick look over with you. You should be able to narrow the price range somewhat after that.
I suppose the bottom line would be something like this;
If you really like it and are prepared to take the risk of it having problems then go for it. You seem to be a very well clued up individual when it comes to calculated risk of purchases.
Good Luck!