Fence higher than 6 feet? That's technically against the law and you need a special permit, but no one cares and contractors will build without one. We're talking about LA, where concrete walls over 10 feet around homes are common.
Pouring more than 30 square feet of concrete, or replacing a driveway? You need a permit. But guess what, yup, contractors will do that without batting an eye.
Replacing a sink or toilet? Yup, you need a permit. Installing a built-in book shelf that technically takes away square footage? You need a permit. New windows? Permit! New showerhead, that's a permit too – yes, actually. And all of these have fees (some of which are more than the cost of the change), inspections, and will be factored into the tax assessment.
These are requirements for both single family homes and multi-family developments. While LA has no shortage of laws on the books, I'm thankful that at least compared to San Francisco contractors have no hesitation cutting right through it. It might have to do with the fact that unlike SF, LA has the space to keep things out of site from overly-nosy neighbors.