as others have said get a workshop to hook up a mechanic oil pressure gauge and get it rechecked if it comes out ok i would consider purchasing the car
mine has rust in the bottom of driver sill and some in the rear wheel arches that i slowly getting worse as i havent treated it (stupid i know) its fairly common now for jap cars to have rust in them as the quality of items isnt as good as it was a couple of years ago so you wont get the best of the best
mine has 98500k's on it and hasnt had one problem yet must say the best car ive had
it mostly comes down to what your happy with, if you think it is ok to you then buy it, if you have doubts then dont we can only offer an opinion but most ppl have been in a similar situation
i bout mine for 14k last yr prob spent about 1k on repairing things and replacing this includes timing belt and aircon stuff ive also spent around 1k on mods and thats all its cost me so far in 12months