Have a pre-purchase inspection done by a garage knowledgeable in Ford products, it will be money well spent, what they find may divert you from buying a "bad car" and or what they find (lack of maintenance or repairs needed) can be used to negotiate price.
We charge $125 but anything found you can use to negotiate price and many times I have told customers do not buy this car!!!!
if you are buying a 1997 ford expedition, look into a "hypertech max" Programmer. In the usa they cost round $325.00 give or take and the reason I say this is the computer in the SUV has to be reprogrammed for your driving habbits bc over the years everything has changed and the specs in the computer are from 1997 and its now 2014. Simple things will confuse your truck as Fuel that you use etc, they are rather finicky SUV's This programmer is "user friendly" watch the dvd and its literally straight forward.