That is the way to go, dont overextend yourself. You will end up letting all your projects suffer. One really good site is better than 10 little sites, IMHO.
Basically you build one site, work on it night and day until it's throwing off enough income and it's pretty much on autopilot, then you launch another one. Rinse, repeat.
kust don't start them all at once, otherwise you mind just wnats to explode, work on a half of dozen or so sites currently.
Quiality over quantity works very well. If you are about to start then don't rush and do 1 by 1 quality sites. In the long term that will pay off good.