At 3.92% interest rate for 30-years fixed with a 20% downpayment that's about $3,400/mo and at $900k property tax is another $6k/year, insurance is less than $100/mo so you net out at less than $4k/mo in PITI. And maintenance you'd hope to check what's wrong with the house before you buy but a new roof costs about $20k so unless you replace a roof a year I doubt you'll be spending over $1000/mo for maintenance, at least I'm not. And 20% is not a sizeable downpayment but the minimum to not have to pay mortgage insurance, a sizeable downpayment is 30%, which in a 30 years fixed means paying less than $3500/mo PITI. Of course if you go with ARMs you'd end up paying even less since interest rates are even lower there. If you can afford the downpayment you'd be paying less than rent in SF most of the time.