I recommend looking through more accredited resources for rentals. Call a property manager and see what s/he has available. There's no commitment in asking around. Another good resource is the San Francisco's Association of Realtors website: http://www.sfrealtors.com/US/Rental-Properties-Listings.html.
Hope this helps!
I have a contact who will find rentals for tenants, but there is a minimum monthly rent and you pay the commission for finding the place.
It will be some work to find it on your own, but it probably is the best way.
Best of luck in the search.
Zephyr Real Estate
BRE No. 01188380