... can he join SN and earn a full-time living or at least some food on the table for him and his family?
A quick scan through the responses to your question so far seems to reveal a consensus that SN probably cannot (yet?) provide for a "full-time living" in most countries.
Something I've been wondering about for quite a while now, is how accurate stackers really track their time spent on (or for) SN. I suspect we don't really want to admit how time-consuming it can become.
Yes, you're right. Sometimes it may take a lot of time. There are many posts that require serious consideration.