what is the going rate in O.C. Calif to rent a room in someones home?

Answer 1

It would depend on a number of factors. Are you willing to help the family with housework or as a nanny, or do you want your privacy? Do you want to live close to the beach, which costs more, or is the north county OK? (I've heard that the south county may also be more affordable, but have not verified that.) Do you want kitchen privileges or a private bathroom? Garage parking? And on and on.

Depending on the situation, I think the rent could range from as low as $400/month to perhaps 3-4 times as much. I suggest you look in the Orange County Register, and in the local Register sections that are published on Thursdays:
http://classified.ocregister.com/Classified/searchRERent.jsp

There are also listings in the Pennysaver:
http://www.pennysaverusa.com/realestate/index.aspx?classcode=278&view=rentals

Another resource is Westside Rentals. In the upper left of their web site do a guest search for property type "shared rentals":
http://www.westsiderentals.com/