5mm is getting pretty low, golf greens are around 3-7mm.
As for the price range, that's probably about right if it's in good shape. Check the condition of the chains and sprockets as they can be expensive to replace. Also have a look around the engine mounting points carefully as the frames are prone to cracking on poorly maintained machines.
You can always post some pictures up of the machine if you'd like some advice prior to purchase. Deejay knows them inside out
