Ignoring comments from those who clearly haven’t read the OP properly.
A bit of vapour at the oil filler cap on a warm engine is perfectly normal. It’s fumes off the hot oil. This gets passed back into the engine and burnt off via the EGR system.
Great flumes of smoke would be an issue.
Turbos whistle. They’re spinning 10x faster than the engine so there’s no great surprise that some noise is generated.
I agree that seeing an engine start from cold can be very informative. But cars can also have hot starting problems too.
I fell for the ‘phonecall’ trick when I bought the Beast. 9-years later and she’s not missed a beat. Outside of service / consumable items, I’ve spent probably £300 on parts.
If you don’t feel comfortable, don’t buy.