In short
San Francisco sits on a peninsula seven kilometres by seven, which explains its density, its hills and the price of its housing. The Golden Gate, Alcatraz and the cable cars are the three landmarks.
The city is the historic heart of the technology industry, and that shapes its economy, its population and its rents.
What it really costs
It is one of the most expensive cities in the world for housing. Accommodation takes more than half a monthly budget, and that decides everything else.
Public transport — Muni, BART — covers the city and the bay well. A car is a handicap: parking is scarce and expensive, and break-ins are frequent.
What nobody tells you
Summer is the wrong season. Fog settles in from June to August and daytime temperatures drop to fifteen degrees. September and October are the warm, clear months.
Break-ins to hire cars are a documented and widespread problem. You leave nothing in a vehicle, boot included.
Homelessness and street drug use are highly visible in some districts, the Tenderloin above all. It is a fact of the city, not an incident.