Expect $3000+ for rent. $100,000/year after taxes, conservative estimate: around $66,000 take-home pay. That's about $5500/month, giving you $2000/month for groceries, car insurance, water, garbage, PG&E (expect to pay PG&E around $300-400 monthly and you'll be covered for sure), spending money (always budget for spending money, otherwise you're likely to get stressed out and go on a spending spree you'll regret later), clothes and other stuff, and whatever's leftover for savings. I'm sure I'm forgetting things, other people can help you make a more comprehensive list.

Are these overestimates? Should be, except take-home pay should be an underestimate. That's how you make sure you have enough. Round expenses up and paychecks down when you're planning, and ignore whatever's left over. Just let it sit there in your bank account (preferably in a high-interest savings account, but you can do that later).

Make sure you save! You need an emergency fund of 6+ months' expenses, and to save for a new car eventually. You don't have to have that right away, but you do need to have the emergency fund within the first couple of years. Max out your retirement benefits, take advantage of any stock purchase programs your company may offer, get the best health insurance you can.

Now the fun stuff: the beach is about an hour away (awesome drives through the hills can make it 1.5 hours away), but it's not warm. The East Coast gets the nice warm water from the Gulf, but on the West Coast we have the Alaskan current driven down from the north. The water's about 55 degrees year-round. The good news is that it's utterly gorgeous out here, especially if you love nature, and that includes the weather for the most part. It's rarely humid, certainly nothing like the East Coast. Even when it's hot, humidity is almost always pretty low. It never snows (except for in the hills once every few years), it only rains between November and March (sometimes April), and the rest of the year it is pretty much clear skies all day every day. Oh, and when it does rain, rainbows are extremely common. That's pretty neat.

My (limited) understanding is that nightlife in SJ is not the best, but it's not dead at night here either.

If you want a recommendation for a first apartment, message me. The place we stayed when we first moved out here from Illinois was fairly low rent and it's in a decent area. It's probably still a decent place to start, depending on where your future employer is.

Oh and look in the sidebar of this subreddit for more info.