So what was Musk's net worth when he was twenty?

Probably less than 0,1 per cent of his net worth today. Possibly less than 0,01 per cent.

Multiplying your net worth by a factor of several thousand is fairly rare, regardless of the circumstances you start in. Most people can't do it, even if they start reasonably well off. For example, Musk's own brother Kimbal couldn't.

> Multiplying your net worth by a factor of several thousand is fairly rare, regardless of the circumstances you start in

lol. No it isn't, maybe if you are born wealthy, but plenty of people have a negative net worth at 20 (no savings yet and student/car loans) and are home owners by 40.

Fair enough. But you are basically agreeing with me that those with non-trivial positive net worth in their youth will find multiplying it by several thousand times harder.

And we should rule out massive inheritance to be fair, too. That can cause sudden large jumps in net worth.

A person having 10 000 USD in their youth (far from wealthy, just not poor) would need to aggregate something like 50 million USD in their fifties. Possible, but rare.