Legal Question in Real Estate Law in California

Sure. Real estate appraisers do it all the time. Don't let the appraiser take pictures and see if you get your loan.

As a general rule, yes. It would be very hard to take a picture that didn't include someone's (private) property unless you were maybe in the middle of a national park, and even then, you couldn't be sure. It's what you do with the pictures after taking them that might, occasionally, get you into trouble.

The previous answers are right, but there are some limitations in most jurisdictions. You are limited in the use of telephoto lenses, and you are limited by trespass law, as well as peeping tom laws.