Condensation in rear lights 2017 Cooper

[Mr-B]

Been toying with the idea of getting a Cooper and went to have a look at one today and noticed condensation in the rear lights (just coming up to its 5th birthday) Is this normal (they all do that Sir) or something not right?

And while I'm here, is there anything else with the manual petrol Cooper that I should be wary of? Known faults/issues reliability problems?

TIA.