You're in the Bay Area???
EXPENSIVE.
My guess would be somewhere between $25-40/hour depending on who you use. This is using somebody doing your project as a "side-job." To hire a contractor in your area, well, the price of poker is going up significantly.
Your best bet is to call some small LICENSED contractors out and have them give you a bid or estimate. Without knowing dimensions, how far the basement is from your panel, etc, there's just no way to give an educated response in terms of price or how long a project will take to complete.
As for horror stories...............
Do a search for the guy that owns the studio in So CA and hired some jackass off the street to remodel his entire operation. Months later it was determined the guy never pulled permits nor had engineered drawings prepared for the work he was doing. Of course, when all this came to light the contractor split never to be seen again. Last I heard the owner was looking at having to hire ANOTHER contractor to finish the job, and his business had been out of commission for something like 6 months at that point.
That's about the worst one I've read around here.