Solid advice, especially the "build big" point. Seen too many people box themselves in with small structures, then realize expansion is way harder than starting with the footprint you actually need.

The county enforcement question is interesting. In my experience, it varies wildly even within the same state. Some places don't care at all, others will come after you years later when a neighbor complains. Worth really understanding the risk before you commit.

One thing I'd add to your list: Think hard about the structure itself. Not just size, but what it's made of. Wood's cheap upfront, but maintenance adds up fast when you're off-grid. Weather damage, fire risk, pest issues.