Ask for any kind of maint records/receipts you can get. Ask if you can have a mechanic of your choice look it over.. You yourself can get a real good general idea how it was maintained by looking it over top to bottom. Loose ujoints, spring hangers, brake chambers/hoses/ shoes and drum are all things you can check in a matter of minutes. While your under there look at frame bolts, wiring looms.. General appearance inside and out can tell you a lot..
Expample:If see wires hanging and spliced its obvious what ever repair was done was done on the fly and none came back to Finnish it.
To have this done or to have inside of motor looked will more then likely be on your dime.
Sorry I can't say if its a wise purchase or not.