Buying advice …

Good day together, since I have to get a used mini (younger model from 2001) for someone in the relatives / must be up to 10 TEUR, I am on your help or need a few tips about the 90, 116 hp and the diesel versions. Best said which years of construction, series or engines etc. should you agree? I am very grateful for every tip and of course also an incentive is desired, no matter what happens to you so spontaneously. How does it look like with the: 1. d both petrol and diesel? 2. Rust problems? 3. gearbox or engine problems? 4. Is the diesel and 90hp version overloaded with the soft?