Old age comparison of the 50k vs 100k mileage cars - the 100k could be in better condition due to servicing / use than a 50k etc.
Also, if you are set on a nismo kit, theres the option of buying a standard car and fitting the kit, cost for kit plus paint could work out if the right standard spec car comes up.
I was looking at costing up a kit+fitting and it seems like it may work out about the same so if the right car came up for the right price its something I would consider. It does seem quite difficult to find the nismo kits at the minute though?