7-8k is a good price range, sub 5k are dogs, 9k plus are ambitious, mines just clocked 151k miles full BMWSH, it was a directors car originally and has very little wear and tear, back seats are pretty much the day they left the factory, I specifically went with one that had a good unworn interior and didn't mind a few stone chips here and there as it's much easier to fix paint than source good condition interior panels. At this age it's always good to go on condtion, I looked at much lower mileage ones sub 100k that looked a lot worse for wear.
Around town it will do 300 miles per tank 20mpg, commute to work which is mainly A roads and a few urban areas 320-350 22ish mpg, motorway run at 80mph 420 miles per tank appx 27 mpg.
Mine is showing signs of a suspension refresh now, creaky suspension, wobble under hard braking etc, it will need new shocks, lower arms, and a few other suspension bits and bobs. At this age they probably all do and it won't be cheap, but I think it's well worth it.