If you purchase an existing home, the Coastal Commission has ZERO jurisdiction over you, UNLESS you decide to do something that would necisitate a Coastal Development Permit. (tear down & rebuild, addition). This is not unusual though, a large percentage of existing homes are legally non-conforming (everywhere, not just within the Coastal Zone). Meaning that they no longer meet setback requirements, height requirements, etc. This is because regulations continue to toughen.

These are always things that should be considered when buying a house. But if you are happy with an existing home, there’s no need to worry about what you can plant, etc. (unless you have HOA regulations, etc). Clearing brush can be tricky but that can be tricky anywhere, not just with Coastal.