I don't make a living but I make $XXX/month. I'd recommend choosing a niche that will have a lot of viewers, make two channels - one focusing on quality and one on quantity with the view to start making money with the quantity one straight away and over a year or two, make the quality one into an authority.
Edit: I make about $1/1k visitors but that's through YouTube directly, not with a network. Should I join a network and do they have different (better paying) ads than AdSense?
I don't think so I have a channel with over 36 000 subsribers and 200 000 daily views, I have been invited by at least 20 networks and I have never even thought about singing up...
Regards