SearchTempest.com got to the point where it was my main gig about 5 years ago, although it's since leveled off. Like anything, you end up being pretty active if you want to continue making that "passive" income. :)
I'd rather not get into specifics, but between SearchTempest and AutoTempest, we've bootstrapped up to a team of four. My goal isn't really to get huge or make a pile of money though; mostly just want to keep it going and being as useful as possible, while keeping up with the times. (We really need to get the sites working better on mobile devices; getting ready to release a fully responsive AutoTempest soon...)
