Moving to SF for YC on two weeks' notice
Book a verified temporary stay, prepare a digital application packet, and tell your network exactly when you arrive and what room you need. Search long-term rooms in parallel, but do not send money before an actual tour and written terms.
Bring only what you need for the first month. Keep cash for deposits, transit, food, and an extension if a room falls through. Map the routes you will use repeatedly.
YC batches are in San Francisco; your housing can be solved in stages.
Source: YC FAQ.