I don't understand.  Which statement are you disagreeing with?

&gt; I feel pretty confident that any person who isn't encumbered by circumstances (like medical issues) can double their hourly wage in a decade, if they focus on it.

whereby 'focus' I mean e.g. the opposite of 'have a kid that you have to take care of'.

or

&gt;  So generally, waiting until your mid-thirties to have a kid, rather than having that kid in your mid-twenties, helps a lot.

?

Like, it's well-known that more wealthy people tend to have children later in life than less wealthy people do.  But the former doesn't make any sense for "&lt;the fact that I think that&gt; is how I know you don't have kids" since it's not related.