I have a real problem calling that water condesation because you said the oil was changed in October. That is only 3 months ago. Now if it had been 3 years; then yes but not in 3 months.
It could be something as simple as the owner has the crankcase breather on upside down and rain water is getting in or a major problem of radiator water leaking into the crankcase.
A radaitor pressure test may not even answer your questions because a lot of internal leaks do not start till the engine is warmed up.
If it were me I would pass.